- Email: [email protected]
APPA at FAIR: From fundamental to applied research
Nuclear Instruments and Methods in Physics Research B 365 (2015) 680–685
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
APPA at FAIR: From fundamental to applied research Th. Stöhlker a,b,c,⇑, V. Bagnoud a,b, K. Blaum d, A. Blazevic a, A. Bräuning-Demian a,e, M. Durante a, F. Herfurth a, M. Lestinsky a, Y. Litvinov a, S. Neff a,f, R. Pleskac a, R. Schuch g, S. Schippers h, D. Severin a, A. Tauschwitz a, C. Trautmann a,f, D. Varentsov a, E. Widmann i, on behalf of the APPA Collaborations a
GSI Helmholtzentrum für Schwerionenforschung, Darmstadt, Germany Helmholtz-Institut Jena, Jena, Germany IOQ, Friedrich-Schiller-Universität Jena, Jena, Germany d Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany e FAIR, Darmstadt, Germany f TU Darmstadt, Darmstadt, Germany g Department of Atomic Physics, Stockholm University, AlbaNova, 10691 Stockholm, Sweden h Justus-Liebig-Universität, 35392 Gießen, Germany i Stefan Meyer Institute, Austrian Academy of Sciences, Vienna, Austria b c
a r t i c l e
i n f o
Article history: Received 11 June 2015 Received in revised form 9 July 2015 Accepted 15 July 2015 Available online 3 September 2015 Keywords: Atomic physics Plasma physics Materials research Biophysics Ions
a b s t r a c t FAIR with its intense beams of ions and antiprotons provides outstanding and worldwide unique experimental conditions for extreme matter research in atomic and plasma physics and for application oriented research in biophysics, medical physics and materials science. The associated research programs comprise interaction of matter with highest electromagnetic fields, properties of plasmas and of solid matter under extreme pressure, density, and temperature conditions, simulation of galactic cosmic radiation, research in nanoscience and charged particle radiotherapy. A broad variety of APPA-dedicated facilities including experimental stations, storage rings, and traps, equipped with most sophisticated instrumentation will allow the APPA community to tackle new challenges. The worldwide most intense source of slow antiprotons will expand the scope of APPA related research to the exciting field of antimatter. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction The APPA pillar, consisting of Atomic and Plasma Physics, and Applied Sciences [1] collaborations with more than 600 scientists from 30 countries, covers a broad variety of highly interdisciplinary research fields, and each represents their own independent research and user community. APPA has been formed to jointly coordinate common experimental installations such as the APPA cave and use synergies in selected research projects. The broad APPA science program will exploit the full parameter range of FAIR beams at different facilities (Fig. 1). Prominent examples for APPA research are
– High-precision tests of bound-state QED in the non-perturbative regime and the determination of fundamental constants. – Creation and probing of dense plasmas for benchmarking theoretical models of planetary and stellar structure. – Emulating galactic cosmic radiation in the laboratory for the assessment of the risks of (manned) space missions. – Investigating the response of materials to extreme irradiation conditions and synthesis of new materials from highly non-equilibrium conditions. – New frontiers in radiotherapy with high-energy charged particles. 2. Atomic physics
⇑ Corresponding author at: GSI Helmholtzentrum für Schwerionenforschung, Darmstadt, Germany. E-mail address: [email protected] (Th. Stöhlker). http://dx.doi.org/10.1016/j.nimb.2015.07.077 0168-583X/Ó 2015 Elsevier B.V. All rights reserved.
The atomic physics research is organized within the two large collaborations SPARC and FLAIR. The SPARC Collaboration for Stored Particle Atomic physics Research (about 320 members) will exploit the unrivaled
Th. Stöhlker et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 680–685
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Examples for highlights of the SPARC program are:
Fig. 1. Experimental facilities at the Modularized Start Version (MSV) of FAIR. The APPA cave houses different experimental stations for APPA experiments.
combination of storage and trapping facilities, a unique feature that distinguishes FAIR from all planned or operating particle accelerators worldwide. FAIR is unique to deliver highly intense, brilliant beams of highly charged heavy ions and radionuclei with excellent momentum definition. As depicted in Fig. 2, the FAIR facilities cover a beam-energy range of more than 10 orders of magnitude [2]. SPARC focuses on the study of atomic matter subject to extreme electromagnetic fields as well as atomic processes mediated by ultrafast electromagnetic interactions. A prominent example for SPARC related research concerns the binding energies of electrons in high-Z one-electron ions where the K-shell electrons are exposed to electric fields (e.g. 1016 V/cm in U91+) close to the Schwinger limit. In a concerted effort and in close collaboration with the leading expert groups in theory, SPARC has initiated a comprehensive research program to accomplish a significant validity check of non-perturbative bound-state QED. We will apply different experimental approaches (1 s Lamb shift, 1s hyperfinestructure, bound-state g-factor, mass measurements) (see e.g. [3]) thus probing QED at different mean-distances of the electron with respect to the nucleus. At the same time SPARC will apply these accurate atomic-physics techniques as powerful tools for the determination of nuclear parameters such as nuclear radii and moments. Even high-precision determination of fundamental constants will be enabled [4,5].
– Using direct beams from SIS100 at the APPA cave for resonant coherent excitation of the ions passing through crystals for precise atomic structure studies (1 s Lamb shift) for all H-like ions up to uranium (possible day-1 experiment) [6]. – At the HESR, the frequencies of novel laser and laser-driven sources in the visible- and the XUV-regime can be boosted by the large c-values to photo-excite heavy ions, allowing to drive inner-shell transitions via lasers (e.g. bound-state QED, nuclear radii, test of time dilatation [7]). – At the HESR, the exploration of correlated electron-dynamics via ultrashort, sub-attosecond fields mediated by ions at large c-values by applying a reaction microscope (e.g. multiple ionization of atoms in kinematically complete fashion, possible day-1 experiment) [8]. – At the HESR, discovery and exploration of a novel pair-production process mediated by electron–electron interaction. A target electron (treated as quasifree) is transferred into a bound state of the projectile via excitation of one electron from the negative Dirac continuum to a bound projectile state (test of relativistic electron-correlation beyond Breit interaction). As a result, the projectile changes its charge-state by two units and a positron is produced (possible day-1 experiment) [9]. – Experiments at relativistic beam energies are complemented by experiments at CRYRING and HITRAP which focus on atomic and nuclear physics of exotic systems at low beam energies (< 10 MeV/u) or even at rest. Both CRYRING and HITRAP are coupled to the ESR which allows to decelerate ions from high energies (400 MeV/u) to the injection energy of both facilities whereby maintaining the high charge-state. This scenario is worldwide unique and will deliver high-accuracy data for bound state QED (avoiding Doppler shifts) as well as the determination of fundamental constants. In addition, atomic collisions can be studied in the non-perturbative, adiabatic regime, and even super-critical fields will get accessible. The FLAIR collaboration (>100 members) proposes the Facility for Low-energy Antiproton and Ion Research. The antimatter physics program at FLAIR is centered around the study of antihydrogen using charged particle traps and spectroscopy of antiprotonic atoms, a research field presently accessible only at CERN. Investigations with antihydrogen atoms focus on precision laser and microwave spectroscopy for stringent tests of CPT invariance, and measurements of the gravitational interaction of antimatter as a test of the weak equivalence principle. Further examples of research addressed by FLAIR are atomic collisions with antiprotons as a clean probe for atomic interactions and the biological effectiveness of antiproton beams at energies of a few 100 MeV. The aforementioned experiments typically require bunched beams of antiprotons. In addition, slowly extracted beams of antiprotons can be provided at FLAIR for setups where coincidence techniques are to be employed, e.g., for nuclear and particle physics type experiments searching for nucleon-meson bound states or using antiprotons as hadronic probes to study nuclear surfaces or halos of stable or short-lived isotopes. Although FLAIR is not part of the Modularized Start Version of FAIR, making use of CRYRING (a Swedish in-kind contribution for FAIR) and HITRAP such antiproton experiments would be feasible if a beamline were available to transfer antiprotons from the production target at FAIR to the ESR. 2.1. Status of experiments
Fig. 2. Portfolio of storage and trapping facilities at FAIR.
SPARC has formed various working groups which develop and construct the equipment and perform precursor experiments at
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the present GSI and suitable external facilities. Prominent examples are micro-calorimeters, a Compton polarimeter, laser systems, as well as electron and gas targets. Moreover, HITRAP has been commissioned in 2014 and the installation of CRYRING at the ESR is progressing well. Both HITRAP and CRYRING will be available for first experiments once SIS18 and the ESR will be in operation again in 2017 [2]. For the HESR, a prototype micro-droplet target is already working at the ESR. Moreover, for the HESR and the CRYRING, various Technical Design Reports (TDR) have been submitted or are in preparation (see SPARC website [1]). Finally, it should be mentioned that the channeling setup provided by the RIKEN and GSI groups was already tested in experiments with U89+ ions at SIS18 [5] and ESR. 3. Bio, medical and materials research Biophysics and materials science are combined in the BIOMAT collaboration (about 110 members) and concern new frontiers in radiotherapy with high-energy charged particles, protection from galactic cosmic radiation in spaceflight, response and reliability of materials exposed to extreme radiation conditions, radiation effects for nuclear waste management, and the application of ion beams in geosciences, mineralogy, nanoscience and other areas. Ion beam research in materials science focuses on interaction processes of relativistic heavy ions with condensed matter. High-Z ions deposit enormous energy densities into the solid and drive the local atomic structure to far from equilibrium resulting in rapid phase transitions and complex structural modifications within a highly localized nanoscale damage zone. Effects include permanent changes of materials properties, local melting, shock waves, emission of secondary particles and the creation of nanostructures. The large penetration depth of the FAIR beams provides homogeneously irradiated thick bulk materials suitable for radiation hardness measurements of macroscopic samples. Moreover, beams of intensities much higher than presently available combined with the large energy deposition of high-Z ions constitute a unique tool to study the behavior of materials exposed to (multiple) extreme conditions. Examples of exiting research topics are:
performing high-resolution (down to almost 10 lm) imaging of the target itself. Theranostics has the additional advantage of removing the uncertainty due to the use of X-rays (CT) for imaging and charged particles for treatment. Preliminary images of a humanoid phantom and complex instruments (see Fig. 4) have shown excellent resolution and proven the feasibility of the modality [14]. – FAIR will be a worldwide unique test bed for using radioactive beams in therapy, for instance 11C, a b+-emitter with the same biophysical characteristics of the 12C stable beam currently used for radiotherapy but able to provide a unique resolution by PET imaging, and therefore a highly precise online visualization of the therapeutic beam. Use of 11C in therapy has been discussed since long time and pilot projects have been carried out in Japan, but so far the beam intensity was too low to get significant results. – Protection of astronauts and electronics in deep space is a major concern in space exploration. Studies on biological effects of cosmic rays, single-event upsets in electronics, and shielding require high-energy accelerators for ground-based testing [15]. The European Space Agency (ESA) has recently launched a study project to define the possible exploitation of FAIR for ESA-related studies, both in material sciences and biophysics. 3.1. Status of experiments Future activities in biophysics, materials science and other related fields will be performed at the multipurpose BIOMAT beamline. It will be established as a worldwide unique user facility with flexible settings for different types of samples, irradiation conditions and sophisticated instrumentation for in-situ and/or on-line monitoring of radiation effects (TDR in preparation). The community is ready to perform day-1 experiments as soon as the APPA cave and the BIOMAT beamline are installed. In materials science day-1 experiments include the irradiation of minerals in high-pressure devices. For biophysics, the day-1 experiment will be the exposure of human cells and tissues to heavy ions at energies around 10 GeV/u, the first tests of these high energies for space radiation protection 4. Plasma physics
– Irradiation experiments under the simultaneous application of extreme pressures and temperatures by using high-pressure cells (Fig. 3) to investigate the effects of radioactive decay events in compressed and heated minerals of Earth’s interior and relate material properties with geodynamic processes [10]. – An exciting application of irradiating solids at high pressure is to modify thermodynamic pathways in the phase diagram such that previously unstable high-pressure phases are recoverable upon pressure release. This allows the synthesis of new materials that are otherwise not accessible [11,12]. – A more practical, but important aspect of materials science with FAIR beams concerns radiation hardness, thermo-mechanical response, and electrical degradation of thick functional bulk materials (e.g. carbon-based high-power targets or beam dumps, collimators, and insulating components) to be applied in high-dose environments at next generation high-power facilities. Specific examples for biophysics research topics include – New ideas for therapy with charged particles at PaNTERA where high-energy protons are applied simultaneously for therapy and radiography (theranostics). The new method, patented at GSI [13], will allow treatment of small, moving targets while
Bunched FAIR beams of highest intensity provide huge energy densities (hundreds of kJ/g) and allow novel experiments and unprecedented diagnostic capabilities. Plasma physics subjects at FAIR are addressed by the HEDgeHOB and WDM collaborations (about 240 scientists). Matter exposed to FAIR beams experiences similar extreme temperature and pressure conditions as prevail in the interiors of stars, brown dwarfs or giant planets (so-called warm dense matter) [16]. The research program will focus on the equation of state and on transport properties of different materials in so far unexplored warm dense matter and high-energy density regions of the phase diagram. Related to these major goals, phase transitions, hydrodynamics and instabilities are of great interest. For instance, particle coupling in dense plasmas changes significantly, leading to different properties that need to be experimentally investigated (see Fig. 5). Sophisticated computational tools have been developed to understand and predict the hydrodynamic processes of ion-beam heated matter. This allows to design special target configurations which enable a precise diagnostics of the target state with a minimum of measured quantities. State of the art optical and laser diagnostics will be applied to improve the understanding of atomic physics and thermodynamic properties of matter under these extreme conditions.
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Fig. 3. Intense FAIR beams are required for high-dose irradiations of highly pressurized solids enclosed between two thick diamond anvils (left). Advanced, heatable highpressure devices (right) provide up to 2000 K and tens of GPa, similar to conditions existing in the Earth mantle.
Fig. 4. The PaNTERA project, a collaboration of biophysics and plasma physics, exploits relativistic protons and the PRIOR setup for therapy. Proton radiograph of human head phantom (800 MeV protons, LANL, 2013) (left) and wristwatch (4 GeV protons, GSI, 2014) (right).
heated by the FAIR beam with an annular focal spot using a RF beam rotator, leading to its subsequent expansion and low entropy compression of the cold inner material [19] to pressures of several Mbar at modest temperatures and hence generating matter as in the interior of planets such as Jupiter, Saturn or Earth. – WDM (Warm Dense Matter) research aims at measuring spectrally resolved opacities at constant target temperature, dynamic confinement [20] with a non-interfering tamper that enables optical investigations in the K- or L-shell bands at constant volume and quasi-static heating at constant pressure.
Fig. 5. Schematic phase diagram showing the areas accessible with FAIR and other facilities as well as the conditions existing in cosmic objects. The red line separates the ideal and dense, strongly coupled plasma regimes (warm dense matter).
The plasma physics collaborations will employ the following experimental frameworks at a dedicated beamline in the APPA cave: – PRIOR is a worldwide unique high-energy proton microscopy facility integrated into the SIS-100 HEDgeHOB beamline, providing both high resolution and large field of view options for fast proton radiography [17]. PRIOR will allow tests of fundamental properties of materials in extreme dynamic environments generated by external drivers and is open for multidisciplinary research projects including plasma physics, materials research and medical physics (see PaNTERA project) [13]. – In HIHEX (Heavy Ion Heating and Expansion) experiments, targets are quickly and uniformly heated by an intense heavy-ions pulse, generating high entropy and high energy density states [18]. After heating, the sample will isentropically expand and pass through various regions of interest in the phase diagram. – LAPLAS (Laboratory Planetary Sciences) experiments will make use of cryogenic targets such as solid hydrogen confined by an outer cylinder of a heavier material. The outside cylinder is
For the completion of the plasma physics research program at FAIR, the availability of a powerful probe (or driver) is essential. This probe can very advantageously be based on a high-energy laser that is matched to the requirements of all four experimental schemes, but also serve a much larger community within APPA. A project to build this laser, the so-called ‘‘Helmholtz Beamline’’, exists on the roadmap of infrastructure of the Helmholtz society and is currently in the planning stage. During this stage GSI together with the Helmholtz center in Dresden Rossendorf and the Helmholtz Institute Jena are conducting the necessary R&D in the fields of laser technology and laser-based diagnostics at their facilities. This includes experimental demonstrations and validations at the PHELIX facility.
4.1. Status of experiments HIHEX, WDM and PRIOR frameworks will be provided in the very beginning of the FAIR operation. The collaborations will be able to start the physics program as soon as the first uranium or proton beam is delivered to the experimental area either by SIS100 or by SIS18. Later, upon the availability of the full intensity SIS100 uranium beams and additional components of the setup (RF beam rotator and penetrating probes) the LAPLAS experiments will join. The TDRs for the most significant components of the experimental setups are approved (large-aperture, high-gradient super-conducting quadruplet) or submitted for review (vacuum target chamber, key diagnostic instruments, diagnostic laser, RF beam rotator and DAQ).
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5. Comparison with other experiments in the field Atomic Physics: For highly-charged heavy ions, FAIR will be worldwide unique with respect to the beam energies and intensities. Fixed target experiments for highly-charged ions at relativistic energies with c > 2 will be available only at FAIR. The main attention will be given to unparalleled experimental opportunities offered by storage rings, namely the large dynamical range from single ions to highest intensities and the excellent beam conditions due to cooling (momentum definition, high luminosity, high detection efficiency, etc.). FAIR will undoubtedly be the world leading laboratory in this field. It will be the only facility offering highly-charged ions of any element up to bare uranium (including radioactive nuclides) in a wide range of energies (see Fig. 2). In particular, for the HESR (cooled ion beams up to c 6) there is no competition in the world and the only comparable ring facility may be constructed within the future HIAF project proposed in China (the HIAF project is still in an initial design phase and its scope is not yet finalized). For the energy range of the ESR, the CSRe ring in Lanzhou (China) can provide comparable experimental conditions only for lower-Z ions up to about xenon. To extend the range of accessible elements, it is in under discussion to replace the driver accelerator in Lanzhou, which, if successful, will provide experimental conditions similar as at the present ESR. However, no deceleration option in the CSRe as well as no low-energy facilities like CRYRING and HITRAP will be available there. Concerning the CRYRING, for low-Z elements up to about titanium, highly-charged ions will be available at the Heidelberg TSR storage ring which is planned to be installed at ISOLDE/CERN. For heavier-Z elements FAIR will remain unique. The low-energy antiproton physics community is making constant progress at the Antiproton Decelerator (AD) of CERN. A significant part of the FLAIR collaboration members is actively involved in running experiments, e.g. measurements on antihydrogen and of the antiproton magnetic moment [21], at the AD of CERN, which is currently the only source for low energy antiprotons world-wide. To cope with these increased activities and to lower the energy from 5 MeV to 100 keV, CERN is constructing an additional deceleration ring called ELENA (completion expected in 2017). These developments demonstrate the rich science case for low-energy antiproton physics as anticipated by the FLAIR collaboration at FAIR. With CRYRING@ESR two fully commissioned storage rings would be available, and, by installing an antiproton transfer line between HESR and ESR, the physics program of the FLAIR collaboration could be realized at a very early stage. One may note that a further important facility for FLAIR, HITRAP at the ESR, has just been commissioned. This portfolio of facilities (CRYRING, HITRAP and the electrostatic storage ring USR) will enable novel physics opportunities such as slowly extracted antiproton beam which are not covered by ELENA at AD.
5.1. Biophysics and materials research There are no facilities comparable to FAIR active in materials science and in biophysical research offering the combination of high-intensity and high-energy heavy ions. In Europe, GANIL in France and therapy facilities (HIT, Germany and CNAO, Italy) are limited to lower energies and beam currents. CERN is planning a biomedical facility at LEIR, which will accelerate only light ions up to 400 MeV/u. The NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory (BNL) in USA is very active in space radiation research, but has no plans for radiotherapy and is limited to 1–2 GeV/u. Moreover, FAIR will accelerate ions at energies much higher than those available at NSRL. These high FAIR energies (5–10 GeV/u) give an important contribution to the
effective dose equivalent in deep space. Biomedical research and materials science is also ongoing in Asia (HIMAC and RIKEN in Japan, IMP–CAS and Shanghai in China), but those facilities have lower energies and beam intensities than at FAIR. 5.2. Plasma physics High energy density states in matter can be generated in the laboratory only using the most powerful drivers such as large laser or Z-pinch facilities, chemical explosives, and gas guns. The most significant information so far has been obtained using shock wave techniques where the material is compressed and irreversibly heated, leading to high values of pressure and entropy. However, with these techniques only a narrow region of the principal and porous shock adiabats has been investigated whereas fascinating areas of the HED phase diagram, including the critical point and strongly coupled plasma regions will remain out of reach. In recent years, a complementary approach to exploit coherent X-ray sources such as the XFEL and LCLS is gaining an important role in investigation of warm dense matter. Samples generated this way are highly transient, typically on the femtosecond scale, where matter passes through very exotic states far from the thermodynamic equilibrium. In contrast, intense ion beams uniformly deposit energy over extended volumes of matter, which enables conditions at the thermodynamic equilibrium to be measured over relatively long time scales. They are thus capable of inducing these exotic states in the target material directly, without the generation of Mbar-pressure shocks. In this view, FAIR offers a unique and extended approach to plasma physics research. Other advantages of using ion beams include the high repetition rate of the driver and high beam-target coupling efficiency for any target material. 6. Summary & conclusions In summary, for the foreseeable future even the Modularized Start Version of FAIR will have unique key features that offer novel, unique, and challenging research opportunities with large discovery potential for the interdisciplinary research fields of APPA. We like to emphasize that research in the different APPA fields is continuously evolving and is not limited to the discovery of a determined endpoint, but rather to increase and to refine our basic knowledge of matter subject to extreme conditions. APPA at FAIR will substantially deepen our scientific knowledge with large impact for applied science such as cancer therapy, space radiation protection, nuclear waste management, geosciences, nanotechnology just to name a few. The same holds true for the physics of warm dense and high energy density plasma as it is essential for, e.g., the understanding of the planetary and stellar structure. Closely linked is the aim to gain in-depth knowledge of atomic interactions where extreme electromagnetic fields prevail. This finally leads to the still open question of the validity of QED in the non-perturbative regime. Moreover, since the start of the FAIR project in 2003, the APPA collaborations have proven a high flexibility by continuously adjusting their research program as well as their instrumentation to the top level questions relevant for the APPA communities. For example, the research program of APPA was severely affected by the introduction of the modularized start version. As a consequence, APPA was seeking for alternatives to maintain the strength of its research program. Indeed, a new strategy was worked out, evaluated and approved and is getting implemented by the installation of CRYRING at the ESR and the use of the HESR for ion beam experiments. Moreover, options are presently investigated by a dedicated study group to allow for experiments with slow antiprotons at CRYRING and HITRAP, the key facilities of FLAIR. Overall we
Th. Stöhlker et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 680–685
are sure that all APPA collaborations will remain at the frontline of their research fields and that all experimental installations for APPA can be expected to be operational when beams from SIS100 will become available. Even more, we expect to start with FAIR related experiments as early as 2017 with the commissioning of CRYRING by using heavy ions from the ESR. Finally we want to stress the importance of a lively research program at the campus of the current GSI/FAIR facility to bridge the long gap until FAIR is fully operational. This appears to us as the key for success of future research at FAIR. Therefore, it is crucial to keep access to the operating GSI facilities including PHELIX, UNILAC and SIS18. This is also required for performing tests and beam time commissioning of the major elements of the experimental installations for FAIR. References [1] Websites of the APPA collaborations.. [2] Th. Stöhlker et al., Hyperfine Interact. 1–9 (2014).
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]
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Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb
APPA at FAIR: From fundamental to applied research Th. Stöhlker a,b,c,⇑, V. Bagnoud a,b, K. Blaum d, A. Blazevic a, A. Bräuning-Demian a,e, M. Durante a, F. Herfurth a, M. Lestinsky a, Y. Litvinov a, S. Neff a,f, R. Pleskac a, R. Schuch g, S. Schippers h, D. Severin a, A. Tauschwitz a, C. Trautmann a,f, D. Varentsov a, E. Widmann i, on behalf of the APPA Collaborations a
GSI Helmholtzentrum für Schwerionenforschung, Darmstadt, Germany Helmholtz-Institut Jena, Jena, Germany IOQ, Friedrich-Schiller-Universität Jena, Jena, Germany d Max-Planck-Institut für Kernphysik, 69117 Heidelberg, Germany e FAIR, Darmstadt, Germany f TU Darmstadt, Darmstadt, Germany g Department of Atomic Physics, Stockholm University, AlbaNova, 10691 Stockholm, Sweden h Justus-Liebig-Universität, 35392 Gießen, Germany i Stefan Meyer Institute, Austrian Academy of Sciences, Vienna, Austria b c
a r t i c l e
i n f o
Article history: Received 11 June 2015 Received in revised form 9 July 2015 Accepted 15 July 2015 Available online 3 September 2015 Keywords: Atomic physics Plasma physics Materials research Biophysics Ions
a b s t r a c t FAIR with its intense beams of ions and antiprotons provides outstanding and worldwide unique experimental conditions for extreme matter research in atomic and plasma physics and for application oriented research in biophysics, medical physics and materials science. The associated research programs comprise interaction of matter with highest electromagnetic fields, properties of plasmas and of solid matter under extreme pressure, density, and temperature conditions, simulation of galactic cosmic radiation, research in nanoscience and charged particle radiotherapy. A broad variety of APPA-dedicated facilities including experimental stations, storage rings, and traps, equipped with most sophisticated instrumentation will allow the APPA community to tackle new challenges. The worldwide most intense source of slow antiprotons will expand the scope of APPA related research to the exciting field of antimatter. Ó 2015 Elsevier B.V. All rights reserved.
1. Introduction The APPA pillar, consisting of Atomic and Plasma Physics, and Applied Sciences [1] collaborations with more than 600 scientists from 30 countries, covers a broad variety of highly interdisciplinary research fields, and each represents their own independent research and user community. APPA has been formed to jointly coordinate common experimental installations such as the APPA cave and use synergies in selected research projects. The broad APPA science program will exploit the full parameter range of FAIR beams at different facilities (Fig. 1). Prominent examples for APPA research are
– High-precision tests of bound-state QED in the non-perturbative regime and the determination of fundamental constants. – Creation and probing of dense plasmas for benchmarking theoretical models of planetary and stellar structure. – Emulating galactic cosmic radiation in the laboratory for the assessment of the risks of (manned) space missions. – Investigating the response of materials to extreme irradiation conditions and synthesis of new materials from highly non-equilibrium conditions. – New frontiers in radiotherapy with high-energy charged particles. 2. Atomic physics
⇑ Corresponding author at: GSI Helmholtzentrum für Schwerionenforschung, Darmstadt, Germany. E-mail address: [email protected] (Th. Stöhlker). http://dx.doi.org/10.1016/j.nimb.2015.07.077 0168-583X/Ó 2015 Elsevier B.V. All rights reserved.
The atomic physics research is organized within the two large collaborations SPARC and FLAIR. The SPARC Collaboration for Stored Particle Atomic physics Research (about 320 members) will exploit the unrivaled
Th. Stöhlker et al. / Nuclear Instruments and Methods in Physics Research B 365 (2015) 680–685
681
Examples for highlights of the SPARC program are:
Fig. 1. Experimental facilities at the Modularized Start Version (MSV) of FAIR. The APPA cave houses different experimental stations for APPA experiments.
combination of storage and trapping facilities, a unique feature that distinguishes FAIR from all planned or operating particle accelerators worldwide. FAIR is unique to deliver highly intense, brilliant beams of highly charged heavy ions and radionuclei with excellent momentum definition. As depicted in Fig. 2, the FAIR facilities cover a beam-energy range of more than 10 orders of magnitude [2]. SPARC focuses on the study of atomic matter subject to extreme electromagnetic fields as well as atomic processes mediated by ultrafast electromagnetic interactions. A prominent example for SPARC related research concerns the binding energies of electrons in high-Z one-electron ions where the K-shell electrons are exposed to electric fields (e.g. 1016 V/cm in U91+) close to the Schwinger limit. In a concerted effort and in close collaboration with the leading expert groups in theory, SPARC has initiated a comprehensive research program to accomplish a significant validity check of non-perturbative bound-state QED. We will apply different experimental approaches (1 s Lamb shift, 1s hyperfinestructure, bound-state g-factor, mass measurements) (see e.g. [3]) thus probing QED at different mean-distances of the electron with respect to the nucleus. At the same time SPARC will apply these accurate atomic-physics techniques as powerful tools for the determination of nuclear parameters such as nuclear radii and moments. Even high-precision determination of fundamental constants will be enabled [4,5].
– Using direct beams from SIS100 at the APPA cave for resonant coherent excitation of the ions passing through crystals for precise atomic structure studies (1 s Lamb shift) for all H-like ions up to uranium (possible day-1 experiment) [6]. – At the HESR, the frequencies of novel laser and laser-driven sources in the visible- and the XUV-regime can be boosted by the large c-values to photo-excite heavy ions, allowing to drive inner-shell transitions via lasers (e.g. bound-state QED, nuclear radii, test of time dilatation [7]). – At the HESR, the exploration of correlated electron-dynamics via ultrashort, sub-attosecond fields mediated by ions at large c-values by applying a reaction microscope (e.g. multiple ionization of atoms in kinematically complete fashion, possible day-1 experiment) [8]. – At the HESR, discovery and exploration of a novel pair-production process mediated by electron–electron interaction. A target electron (treated as quasifree) is transferred into a bound state of the projectile via excitation of one electron from the negative Dirac continuum to a bound projectile state (test of relativistic electron-correlation beyond Breit interaction). As a result, the projectile changes its charge-state by two units and a positron is produced (possible day-1 experiment) [9]. – Experiments at relativistic beam energies are complemented by experiments at CRYRING and HITRAP which focus on atomic and nuclear physics of exotic systems at low beam energies (< 10 MeV/u) or even at rest. Both CRYRING and HITRAP are coupled to the ESR which allows to decelerate ions from high energies (400 MeV/u) to the injection energy of both facilities whereby maintaining the high charge-state. This scenario is worldwide unique and will deliver high-accuracy data for bound state QED (avoiding Doppler shifts) as well as the determination of fundamental constants. In addition, atomic collisions can be studied in the non-perturbative, adiabatic regime, and even super-critical fields will get accessible. The FLAIR collaboration (>100 members) proposes the Facility for Low-energy Antiproton and Ion Research. The antimatter physics program at FLAIR is centered around the study of antihydrogen using charged particle traps and spectroscopy of antiprotonic atoms, a research field presently accessible only at CERN. Investigations with antihydrogen atoms focus on precision laser and microwave spectroscopy for stringent tests of CPT invariance, and measurements of the gravitational interaction of antimatter as a test of the weak equivalence principle. Further examples of research addressed by FLAIR are atomic collisions with antiprotons as a clean probe for atomic interactions and the biological effectiveness of antiproton beams at energies of a few 100 MeV. The aforementioned experiments typically require bunched beams of antiprotons. In addition, slowly extracted beams of antiprotons can be provided at FLAIR for setups where coincidence techniques are to be employed, e.g., for nuclear and particle physics type experiments searching for nucleon-meson bound states or using antiprotons as hadronic probes to study nuclear surfaces or halos of stable or short-lived isotopes. Although FLAIR is not part of the Modularized Start Version of FAIR, making use of CRYRING (a Swedish in-kind contribution for FAIR) and HITRAP such antiproton experiments would be feasible if a beamline were available to transfer antiprotons from the production target at FAIR to the ESR. 2.1. Status of experiments
Fig. 2. Portfolio of storage and trapping facilities at FAIR.
SPARC has formed various working groups which develop and construct the equipment and perform precursor experiments at
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the present GSI and suitable external facilities. Prominent examples are micro-calorimeters, a Compton polarimeter, laser systems, as well as electron and gas targets. Moreover, HITRAP has been commissioned in 2014 and the installation of CRYRING at the ESR is progressing well. Both HITRAP and CRYRING will be available for first experiments once SIS18 and the ESR will be in operation again in 2017 [2]. For the HESR, a prototype micro-droplet target is already working at the ESR. Moreover, for the HESR and the CRYRING, various Technical Design Reports (TDR) have been submitted or are in preparation (see SPARC website [1]). Finally, it should be mentioned that the channeling setup provided by the RIKEN and GSI groups was already tested in experiments with U89+ ions at SIS18 [5] and ESR. 3. Bio, medical and materials research Biophysics and materials science are combined in the BIOMAT collaboration (about 110 members) and concern new frontiers in radiotherapy with high-energy charged particles, protection from galactic cosmic radiation in spaceflight, response and reliability of materials exposed to extreme radiation conditions, radiation effects for nuclear waste management, and the application of ion beams in geosciences, mineralogy, nanoscience and other areas. Ion beam research in materials science focuses on interaction processes of relativistic heavy ions with condensed matter. High-Z ions deposit enormous energy densities into the solid and drive the local atomic structure to far from equilibrium resulting in rapid phase transitions and complex structural modifications within a highly localized nanoscale damage zone. Effects include permanent changes of materials properties, local melting, shock waves, emission of secondary particles and the creation of nanostructures. The large penetration depth of the FAIR beams provides homogeneously irradiated thick bulk materials suitable for radiation hardness measurements of macroscopic samples. Moreover, beams of intensities much higher than presently available combined with the large energy deposition of high-Z ions constitute a unique tool to study the behavior of materials exposed to (multiple) extreme conditions. Examples of exiting research topics are:
performing high-resolution (down to almost 10 lm) imaging of the target itself. Theranostics has the additional advantage of removing the uncertainty due to the use of X-rays (CT) for imaging and charged particles for treatment. Preliminary images of a humanoid phantom and complex instruments (see Fig. 4) have shown excellent resolution and proven the feasibility of the modality [14]. – FAIR will be a worldwide unique test bed for using radioactive beams in therapy, for instance 11C, a b+-emitter with the same biophysical characteristics of the 12C stable beam currently used for radiotherapy but able to provide a unique resolution by PET imaging, and therefore a highly precise online visualization of the therapeutic beam. Use of 11C in therapy has been discussed since long time and pilot projects have been carried out in Japan, but so far the beam intensity was too low to get significant results. – Protection of astronauts and electronics in deep space is a major concern in space exploration. Studies on biological effects of cosmic rays, single-event upsets in electronics, and shielding require high-energy accelerators for ground-based testing [15]. The European Space Agency (ESA) has recently launched a study project to define the possible exploitation of FAIR for ESA-related studies, both in material sciences and biophysics. 3.1. Status of experiments Future activities in biophysics, materials science and other related fields will be performed at the multipurpose BIOMAT beamline. It will be established as a worldwide unique user facility with flexible settings for different types of samples, irradiation conditions and sophisticated instrumentation for in-situ and/or on-line monitoring of radiation effects (TDR in preparation). The community is ready to perform day-1 experiments as soon as the APPA cave and the BIOMAT beamline are installed. In materials science day-1 experiments include the irradiation of minerals in high-pressure devices. For biophysics, the day-1 experiment will be the exposure of human cells and tissues to heavy ions at energies around 10 GeV/u, the first tests of these high energies for space radiation protection 4. Plasma physics
– Irradiation experiments under the simultaneous application of extreme pressures and temperatures by using high-pressure cells (Fig. 3) to investigate the effects of radioactive decay events in compressed and heated minerals of Earth’s interior and relate material properties with geodynamic processes [10]. – An exciting application of irradiating solids at high pressure is to modify thermodynamic pathways in the phase diagram such that previously unstable high-pressure phases are recoverable upon pressure release. This allows the synthesis of new materials that are otherwise not accessible [11,12]. – A more practical, but important aspect of materials science with FAIR beams concerns radiation hardness, thermo-mechanical response, and electrical degradation of thick functional bulk materials (e.g. carbon-based high-power targets or beam dumps, collimators, and insulating components) to be applied in high-dose environments at next generation high-power facilities. Specific examples for biophysics research topics include – New ideas for therapy with charged particles at PaNTERA where high-energy protons are applied simultaneously for therapy and radiography (theranostics). The new method, patented at GSI [13], will allow treatment of small, moving targets while
Bunched FAIR beams of highest intensity provide huge energy densities (hundreds of kJ/g) and allow novel experiments and unprecedented diagnostic capabilities. Plasma physics subjects at FAIR are addressed by the HEDgeHOB and WDM collaborations (about 240 scientists). Matter exposed to FAIR beams experiences similar extreme temperature and pressure conditions as prevail in the interiors of stars, brown dwarfs or giant planets (so-called warm dense matter) [16]. The research program will focus on the equation of state and on transport properties of different materials in so far unexplored warm dense matter and high-energy density regions of the phase diagram. Related to these major goals, phase transitions, hydrodynamics and instabilities are of great interest. For instance, particle coupling in dense plasmas changes significantly, leading to different properties that need to be experimentally investigated (see Fig. 5). Sophisticated computational tools have been developed to understand and predict the hydrodynamic processes of ion-beam heated matter. This allows to design special target configurations which enable a precise diagnostics of the target state with a minimum of measured quantities. State of the art optical and laser diagnostics will be applied to improve the understanding of atomic physics and thermodynamic properties of matter under these extreme conditions.
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Fig. 3. Intense FAIR beams are required for high-dose irradiations of highly pressurized solids enclosed between two thick diamond anvils (left). Advanced, heatable highpressure devices (right) provide up to 2000 K and tens of GPa, similar to conditions existing in the Earth mantle.
Fig. 4. The PaNTERA project, a collaboration of biophysics and plasma physics, exploits relativistic protons and the PRIOR setup for therapy. Proton radiograph of human head phantom (800 MeV protons, LANL, 2013) (left) and wristwatch (4 GeV protons, GSI, 2014) (right).
heated by the FAIR beam with an annular focal spot using a RF beam rotator, leading to its subsequent expansion and low entropy compression of the cold inner material [19] to pressures of several Mbar at modest temperatures and hence generating matter as in the interior of planets such as Jupiter, Saturn or Earth. – WDM (Warm Dense Matter) research aims at measuring spectrally resolved opacities at constant target temperature, dynamic confinement [20] with a non-interfering tamper that enables optical investigations in the K- or L-shell bands at constant volume and quasi-static heating at constant pressure.
Fig. 5. Schematic phase diagram showing the areas accessible with FAIR and other facilities as well as the conditions existing in cosmic objects. The red line separates the ideal and dense, strongly coupled plasma regimes (warm dense matter).
The plasma physics collaborations will employ the following experimental frameworks at a dedicated beamline in the APPA cave: – PRIOR is a worldwide unique high-energy proton microscopy facility integrated into the SIS-100 HEDgeHOB beamline, providing both high resolution and large field of view options for fast proton radiography [17]. PRIOR will allow tests of fundamental properties of materials in extreme dynamic environments generated by external drivers and is open for multidisciplinary research projects including plasma physics, materials research and medical physics (see PaNTERA project) [13]. – In HIHEX (Heavy Ion Heating and Expansion) experiments, targets are quickly and uniformly heated by an intense heavy-ions pulse, generating high entropy and high energy density states [18]. After heating, the sample will isentropically expand and pass through various regions of interest in the phase diagram. – LAPLAS (Laboratory Planetary Sciences) experiments will make use of cryogenic targets such as solid hydrogen confined by an outer cylinder of a heavier material. The outside cylinder is
For the completion of the plasma physics research program at FAIR, the availability of a powerful probe (or driver) is essential. This probe can very advantageously be based on a high-energy laser that is matched to the requirements of all four experimental schemes, but also serve a much larger community within APPA. A project to build this laser, the so-called ‘‘Helmholtz Beamline’’, exists on the roadmap of infrastructure of the Helmholtz society and is currently in the planning stage. During this stage GSI together with the Helmholtz center in Dresden Rossendorf and the Helmholtz Institute Jena are conducting the necessary R&D in the fields of laser technology and laser-based diagnostics at their facilities. This includes experimental demonstrations and validations at the PHELIX facility.
4.1. Status of experiments HIHEX, WDM and PRIOR frameworks will be provided in the very beginning of the FAIR operation. The collaborations will be able to start the physics program as soon as the first uranium or proton beam is delivered to the experimental area either by SIS100 or by SIS18. Later, upon the availability of the full intensity SIS100 uranium beams and additional components of the setup (RF beam rotator and penetrating probes) the LAPLAS experiments will join. The TDRs for the most significant components of the experimental setups are approved (large-aperture, high-gradient super-conducting quadruplet) or submitted for review (vacuum target chamber, key diagnostic instruments, diagnostic laser, RF beam rotator and DAQ).
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5. Comparison with other experiments in the field Atomic Physics: For highly-charged heavy ions, FAIR will be worldwide unique with respect to the beam energies and intensities. Fixed target experiments for highly-charged ions at relativistic energies with c > 2 will be available only at FAIR. The main attention will be given to unparalleled experimental opportunities offered by storage rings, namely the large dynamical range from single ions to highest intensities and the excellent beam conditions due to cooling (momentum definition, high luminosity, high detection efficiency, etc.). FAIR will undoubtedly be the world leading laboratory in this field. It will be the only facility offering highly-charged ions of any element up to bare uranium (including radioactive nuclides) in a wide range of energies (see Fig. 2). In particular, for the HESR (cooled ion beams up to c 6) there is no competition in the world and the only comparable ring facility may be constructed within the future HIAF project proposed in China (the HIAF project is still in an initial design phase and its scope is not yet finalized). For the energy range of the ESR, the CSRe ring in Lanzhou (China) can provide comparable experimental conditions only for lower-Z ions up to about xenon. To extend the range of accessible elements, it is in under discussion to replace the driver accelerator in Lanzhou, which, if successful, will provide experimental conditions similar as at the present ESR. However, no deceleration option in the CSRe as well as no low-energy facilities like CRYRING and HITRAP will be available there. Concerning the CRYRING, for low-Z elements up to about titanium, highly-charged ions will be available at the Heidelberg TSR storage ring which is planned to be installed at ISOLDE/CERN. For heavier-Z elements FAIR will remain unique. The low-energy antiproton physics community is making constant progress at the Antiproton Decelerator (AD) of CERN. A significant part of the FLAIR collaboration members is actively involved in running experiments, e.g. measurements on antihydrogen and of the antiproton magnetic moment [21], at the AD of CERN, which is currently the only source for low energy antiprotons world-wide. To cope with these increased activities and to lower the energy from 5 MeV to 100 keV, CERN is constructing an additional deceleration ring called ELENA (completion expected in 2017). These developments demonstrate the rich science case for low-energy antiproton physics as anticipated by the FLAIR collaboration at FAIR. With CRYRING@ESR two fully commissioned storage rings would be available, and, by installing an antiproton transfer line between HESR and ESR, the physics program of the FLAIR collaboration could be realized at a very early stage. One may note that a further important facility for FLAIR, HITRAP at the ESR, has just been commissioned. This portfolio of facilities (CRYRING, HITRAP and the electrostatic storage ring USR) will enable novel physics opportunities such as slowly extracted antiproton beam which are not covered by ELENA at AD.
5.1. Biophysics and materials research There are no facilities comparable to FAIR active in materials science and in biophysical research offering the combination of high-intensity and high-energy heavy ions. In Europe, GANIL in France and therapy facilities (HIT, Germany and CNAO, Italy) are limited to lower energies and beam currents. CERN is planning a biomedical facility at LEIR, which will accelerate only light ions up to 400 MeV/u. The NASA Space Radiation Laboratory (NSRL) at the Brookhaven National Laboratory (BNL) in USA is very active in space radiation research, but has no plans for radiotherapy and is limited to 1–2 GeV/u. Moreover, FAIR will accelerate ions at energies much higher than those available at NSRL. These high FAIR energies (5–10 GeV/u) give an important contribution to the
effective dose equivalent in deep space. Biomedical research and materials science is also ongoing in Asia (HIMAC and RIKEN in Japan, IMP–CAS and Shanghai in China), but those facilities have lower energies and beam intensities than at FAIR. 5.2. Plasma physics High energy density states in matter can be generated in the laboratory only using the most powerful drivers such as large laser or Z-pinch facilities, chemical explosives, and gas guns. The most significant information so far has been obtained using shock wave techniques where the material is compressed and irreversibly heated, leading to high values of pressure and entropy. However, with these techniques only a narrow region of the principal and porous shock adiabats has been investigated whereas fascinating areas of the HED phase diagram, including the critical point and strongly coupled plasma regions will remain out of reach. In recent years, a complementary approach to exploit coherent X-ray sources such as the XFEL and LCLS is gaining an important role in investigation of warm dense matter. Samples generated this way are highly transient, typically on the femtosecond scale, where matter passes through very exotic states far from the thermodynamic equilibrium. In contrast, intense ion beams uniformly deposit energy over extended volumes of matter, which enables conditions at the thermodynamic equilibrium to be measured over relatively long time scales. They are thus capable of inducing these exotic states in the target material directly, without the generation of Mbar-pressure shocks. In this view, FAIR offers a unique and extended approach to plasma physics research. Other advantages of using ion beams include the high repetition rate of the driver and high beam-target coupling efficiency for any target material. 6. Summary & conclusions In summary, for the foreseeable future even the Modularized Start Version of FAIR will have unique key features that offer novel, unique, and challenging research opportunities with large discovery potential for the interdisciplinary research fields of APPA. We like to emphasize that research in the different APPA fields is continuously evolving and is not limited to the discovery of a determined endpoint, but rather to increase and to refine our basic knowledge of matter subject to extreme conditions. APPA at FAIR will substantially deepen our scientific knowledge with large impact for applied science such as cancer therapy, space radiation protection, nuclear waste management, geosciences, nanotechnology just to name a few. The same holds true for the physics of warm dense and high energy density plasma as it is essential for, e.g., the understanding of the planetary and stellar structure. Closely linked is the aim to gain in-depth knowledge of atomic interactions where extreme electromagnetic fields prevail. This finally leads to the still open question of the validity of QED in the non-perturbative regime. Moreover, since the start of the FAIR project in 2003, the APPA collaborations have proven a high flexibility by continuously adjusting their research program as well as their instrumentation to the top level questions relevant for the APPA communities. For example, the research program of APPA was severely affected by the introduction of the modularized start version. As a consequence, APPA was seeking for alternatives to maintain the strength of its research program. Indeed, a new strategy was worked out, evaluated and approved and is getting implemented by the installation of CRYRING at the ESR and the use of the HESR for ion beam experiments. Moreover, options are presently investigated by a dedicated study group to allow for experiments with slow antiprotons at CRYRING and HITRAP, the key facilities of FLAIR. Overall we
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are sure that all APPA collaborations will remain at the frontline of their research fields and that all experimental installations for APPA can be expected to be operational when beams from SIS100 will become available. Even more, we expect to start with FAIR related experiments as early as 2017 with the commissioning of CRYRING by using heavy ions from the ESR. Finally we want to stress the importance of a lively research program at the campus of the current GSI/FAIR facility to bridge the long gap until FAIR is fully operational. This appears to us as the key for success of future research at FAIR. Therefore, it is crucial to keep access to the operating GSI facilities including PHELIX, UNILAC and SIS18. This is also required for performing tests and beam time commissioning of the major elements of the experimental installations for FAIR. References [1] Websites of the APPA collaborations.
[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]
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