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Charge states distributions of lead ions in Al and Cu
Results in Physics 6 (2016) 536–537
Contents lists available at ScienceDirect
Results in Physics journal homepage: www.journals.elsevier.com/results-in-physics
Microarticle
Charge states distributions of lead ions in Al and Cu Shadi Salem ⇑ University of Dammam, Dammam 31441, Saudi Arabia Al-Balqa Applied University, Al-Salt 19117, Jordan
a r t i c l e
i n f o
Article history: Received 21 June 2016 Accepted 6 August 2016 Available online 11 August 2016 Keywords: Ion-atom collisions Relativistic energy Equilibrium charge-state
a b s t r a c t This paper presents the theoretical calculations of the charge-state distributions of relativistic lead ions penetrating through different solid targets, namely, aluminum and copper. Using GLOBAL program, the charge state distributions were calculated. GLOBAL is a program developed at GSI in Darmstadt which calculates various physical quantities characterizing the slowing down of protons and heavy ions in matter for specific kinetic energies ranging from 1 keV/u to 450 GeV/u. The energies used for the calculations of the charge-state distributions are 100, 110, and 170 MeV/u. It was found that the aluminum foil of 15 mg/cm2 thickness is the best stripper can be used to produce the H-like lead (+81), He-like lead (+80) and Li-like lead (+79) ions which have been selected out 72%, 16% and 11%, respectively, of the emerging beam. Ó 2016 The Author. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Introduction Ion-atom collisions are a class of physical phenomena in which radiation can be emitted when energetic charged ion impinges on a neutral atomic system. During Ion-atom collisions, the excitation and/or the ionization of bound electrons of the collision partners can occur and also electrons can be transferred from one collision partner to the other. State selective atomic–collision experiments, such as radiative transfer and excitation RTE and other basic processes measurements [1,2], require known initial charge states. The initial charge states: the bare, H-, He-, and Li-like High-Z projectiles ions for high-energy can be produced using very complicated accelerator. For example, GSI Accelerator facility in Darmstadt can provide the researcher with the projectile nuclear charge for the required energy for the experiment purposes. To achieve the highest required charge state, the stripper foils can be prepared with a certain thickness and placed in the target positions. The modeling of charge-state distributions of ion beams passing through matter requires the knowledge of the basic interaction mechanisms between highly charged ions and neutral atoms, namely, the projectile excitation, de-excitation, ionization, and electron capture into empty projectile states. For heavy ions, many charge states typically contribute to the charge-state distribution. Thus one needs to know all the relevant cross-sections for excitation, ionization and capture for all contributing ground state and excited states. In general, for relativistic heavy ions the situation is simplified compared to low energies due to the fact that the ⇑ Address: University of Dammam, Dammam 31441, Saudi Arabia.
heaviest ions carry only few electrons during their passage through matter. Fig. 1 shows the theoretical results obtained for initially Pb28+ with an incident energy of 170 MeV/u bombarded on aluminum stripper for different thicknesses up to 50 mg/cm2. The results shown in Fig. 1 were obtained using the GLOBAL program which has ability to calculate ionic charge-state distributions of relativistic projectiles traversing solid and gaseous targets. The program is applicable for the interaction of projectiles having a nuclear charge number Z larger than 28 with any target. Details of the underlying physics as well as of a comparison between experiment and predictions by GLOBAL can be found in Ref. [3]. Fig. 1 represents the output of the equilibrium charge-state distributions formed: bare, H-, He-, and Li like lead ions. It is noted from Fig. 1 that the highest charge-state formed, with a percentage of 72% at Al thickness of 15 mg/cm2, is helium-like lead ions. The incident energy for incoming charge state was 168.2 MeV/u, where the energy loss is 1.8 MeV/u. The fraction of the charge-states formed is represented in Fig. 2. The formation of these charge states confirm that the cross sections for ionization is much high and dominant for Al target in which the nuclear charge of target is much smaller than that of the projectile (ZT ZP). The ionization of the projectile ions can be reasonably described within first-order perturbation theory, such as the semi-classical approximation (SCA). For completeness, different entrance energies of the projectile lead ions were involved for the charge-state distributions estimations. Fig. 3 represents the charge-state distributions (He-like lead ions) for incident energies of 100, 110, and 170 MeV. One can notice that the highest charge-state for all energies achieves at thickness of 15 mg/cm2.
E-mail address: [email protected] http://dx.doi.org/10.1016/j.rinp.2016.08.009 2211-3797/Ó 2016 The Author. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
S. Salem / Results in Physics 6 (2016) 536–537
537
Fig. 1. Equilibrium charge-state distributions of lead ions formed after Al foils stripper for different thicknesses at the incident energy of 170 MeV/u.
Fig. 3. Formation of He-like lead ions after Al foils stripper at different thicknesses for incident energies of 100, 110, and 170 MeV/u.
Fig. 2. Equilibrium charge-state fraction at an energy of 170 MeV/u.
For comparison, the GLOBAL program was used to produce the charge-state distributions for different solid target. Equilibrium charge-state of He-like lead ions for copper target (ZT = 29) are represented in Fig. 4. The highest charge-state produced in this case is 52% and 65% for the incident energies of 110 MeV/u and 170 MeV/ u, respectively. Due to the fact the high atomic density in a solid target Cu, the charge-changing effects caused by sequential collisions in the target can be considered. In addition, the crosssections of excitation are more dominant which is not the case for the aluminum target. For light stripper foils, capture is negligible compared to loss for the M-, L-, and possibly K-shells of the ions. Simply it can be concluded that the aluminum target is the proper stripper to produce the highest He-like lead ions with a percentage of 72% of the incoming beams. From these results, it is possible to conclude that the choice of proper stripper thickness for the highest charge-state desired can be obtained. References [1] Tanis JA, Graham WG, Bernkner KH, Bernstein EM, Clark MW, Feinberg B, McMahan MA, Morgan TJ, Rathbun W, Schlachter AS. Resonant transfer excitation in U89+ + C and U90++ H2 collisions. Nucl Instrum Methods B 1991;53:442–7.
Fig. 4. Formation of He-like lead ions after Cu foils stripper at different thicknesses for incident energies of 110, and 170 MeV/u.
[2] Verma P, Mokler PH, Braeuning-Demian A, Braeuning H, Berdermann E, Chatterjee S, Gumberidze A, Hagmann S, Kozhuharov C, Orsic-Muthig A, Reuschl R, Schoeffler M, Spillmann U, Stoehlker Th, Stachura Z, Tashenov S, Wahab MA. Charge exchange and X-ray emission in 70 MeV/u Bi-Au collisions. Nucl Instrum Methods B 2005;235:309–14. [3] Scheidenberger C, Stoehlker Th, Meyerhof WE, Geissel H, Mokler PH, Blank B. Charge states of relativistic heavy ions in matter. Nucl Instrum Methods B 1998;142:441–62.
Contents lists available at ScienceDirect
Results in Physics journal homepage: www.journals.elsevier.com/results-in-physics
Microarticle
Charge states distributions of lead ions in Al and Cu Shadi Salem ⇑ University of Dammam, Dammam 31441, Saudi Arabia Al-Balqa Applied University, Al-Salt 19117, Jordan
a r t i c l e
i n f o
Article history: Received 21 June 2016 Accepted 6 August 2016 Available online 11 August 2016 Keywords: Ion-atom collisions Relativistic energy Equilibrium charge-state
a b s t r a c t This paper presents the theoretical calculations of the charge-state distributions of relativistic lead ions penetrating through different solid targets, namely, aluminum and copper. Using GLOBAL program, the charge state distributions were calculated. GLOBAL is a program developed at GSI in Darmstadt which calculates various physical quantities characterizing the slowing down of protons and heavy ions in matter for specific kinetic energies ranging from 1 keV/u to 450 GeV/u. The energies used for the calculations of the charge-state distributions are 100, 110, and 170 MeV/u. It was found that the aluminum foil of 15 mg/cm2 thickness is the best stripper can be used to produce the H-like lead (+81), He-like lead (+80) and Li-like lead (+79) ions which have been selected out 72%, 16% and 11%, respectively, of the emerging beam. Ó 2016 The Author. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Introduction Ion-atom collisions are a class of physical phenomena in which radiation can be emitted when energetic charged ion impinges on a neutral atomic system. During Ion-atom collisions, the excitation and/or the ionization of bound electrons of the collision partners can occur and also electrons can be transferred from one collision partner to the other. State selective atomic–collision experiments, such as radiative transfer and excitation RTE and other basic processes measurements [1,2], require known initial charge states. The initial charge states: the bare, H-, He-, and Li-like High-Z projectiles ions for high-energy can be produced using very complicated accelerator. For example, GSI Accelerator facility in Darmstadt can provide the researcher with the projectile nuclear charge for the required energy for the experiment purposes. To achieve the highest required charge state, the stripper foils can be prepared with a certain thickness and placed in the target positions. The modeling of charge-state distributions of ion beams passing through matter requires the knowledge of the basic interaction mechanisms between highly charged ions and neutral atoms, namely, the projectile excitation, de-excitation, ionization, and electron capture into empty projectile states. For heavy ions, many charge states typically contribute to the charge-state distribution. Thus one needs to know all the relevant cross-sections for excitation, ionization and capture for all contributing ground state and excited states. In general, for relativistic heavy ions the situation is simplified compared to low energies due to the fact that the ⇑ Address: University of Dammam, Dammam 31441, Saudi Arabia.
heaviest ions carry only few electrons during their passage through matter. Fig. 1 shows the theoretical results obtained for initially Pb28+ with an incident energy of 170 MeV/u bombarded on aluminum stripper for different thicknesses up to 50 mg/cm2. The results shown in Fig. 1 were obtained using the GLOBAL program which has ability to calculate ionic charge-state distributions of relativistic projectiles traversing solid and gaseous targets. The program is applicable for the interaction of projectiles having a nuclear charge number Z larger than 28 with any target. Details of the underlying physics as well as of a comparison between experiment and predictions by GLOBAL can be found in Ref. [3]. Fig. 1 represents the output of the equilibrium charge-state distributions formed: bare, H-, He-, and Li like lead ions. It is noted from Fig. 1 that the highest charge-state formed, with a percentage of 72% at Al thickness of 15 mg/cm2, is helium-like lead ions. The incident energy for incoming charge state was 168.2 MeV/u, where the energy loss is 1.8 MeV/u. The fraction of the charge-states formed is represented in Fig. 2. The formation of these charge states confirm that the cross sections for ionization is much high and dominant for Al target in which the nuclear charge of target is much smaller than that of the projectile (ZT ZP). The ionization of the projectile ions can be reasonably described within first-order perturbation theory, such as the semi-classical approximation (SCA). For completeness, different entrance energies of the projectile lead ions were involved for the charge-state distributions estimations. Fig. 3 represents the charge-state distributions (He-like lead ions) for incident energies of 100, 110, and 170 MeV. One can notice that the highest charge-state for all energies achieves at thickness of 15 mg/cm2.
E-mail address: [email protected] http://dx.doi.org/10.1016/j.rinp.2016.08.009 2211-3797/Ó 2016 The Author. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
S. Salem / Results in Physics 6 (2016) 536–537
537
Fig. 1. Equilibrium charge-state distributions of lead ions formed after Al foils stripper for different thicknesses at the incident energy of 170 MeV/u.
Fig. 3. Formation of He-like lead ions after Al foils stripper at different thicknesses for incident energies of 100, 110, and 170 MeV/u.
Fig. 2. Equilibrium charge-state fraction at an energy of 170 MeV/u.
For comparison, the GLOBAL program was used to produce the charge-state distributions for different solid target. Equilibrium charge-state of He-like lead ions for copper target (ZT = 29) are represented in Fig. 4. The highest charge-state produced in this case is 52% and 65% for the incident energies of 110 MeV/u and 170 MeV/ u, respectively. Due to the fact the high atomic density in a solid target Cu, the charge-changing effects caused by sequential collisions in the target can be considered. In addition, the crosssections of excitation are more dominant which is not the case for the aluminum target. For light stripper foils, capture is negligible compared to loss for the M-, L-, and possibly K-shells of the ions. Simply it can be concluded that the aluminum target is the proper stripper to produce the highest He-like lead ions with a percentage of 72% of the incoming beams. From these results, it is possible to conclude that the choice of proper stripper thickness for the highest charge-state desired can be obtained. References [1] Tanis JA, Graham WG, Bernkner KH, Bernstein EM, Clark MW, Feinberg B, McMahan MA, Morgan TJ, Rathbun W, Schlachter AS. Resonant transfer excitation in U89+ + C and U90++ H2 collisions. Nucl Instrum Methods B 1991;53:442–7.
Fig. 4. Formation of He-like lead ions after Cu foils stripper at different thicknesses for incident energies of 110, and 170 MeV/u.
[2] Verma P, Mokler PH, Braeuning-Demian A, Braeuning H, Berdermann E, Chatterjee S, Gumberidze A, Hagmann S, Kozhuharov C, Orsic-Muthig A, Reuschl R, Schoeffler M, Spillmann U, Stoehlker Th, Stachura Z, Tashenov S, Wahab MA. Charge exchange and X-ray emission in 70 MeV/u Bi-Au collisions. Nucl Instrum Methods B 2005;235:309–14. [3] Scheidenberger C, Stoehlker Th, Meyerhof WE, Geissel H, Mokler PH, Blank B. Charge states of relativistic heavy ions in matter. Nucl Instrum Methods B 1998;142:441–62.