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The optics of the exotic beam line at LNL
Nuclear Physics A 746 (2004) 389c–392c
The optics of the exotic beam line at LNL V.Z. Maidikova , T. Glodariub∗ , M. La Commarac , M. Sandolic , C. Signorinid , L. Costae , F. Soramelf , R. Bonettig , A. De Rosac , M. Di Pietroc , A. Guglielmettig , G. Inglimac , B. Martinc , M. Mazzoccod , D. Pierroutsakouc , M. Romolic , P. Scopeld , and L. Stroee∗ a
Institute for Nuclear Research, National Academy of Sciences, 06380 Kiev, Ukraine
b
Physics Department, University of Padova and INFN-LNL, I-35131 Padova, Italy
c
Physics Department, University of Napoli and INFN, I-80125 Napoli, Italy
d e f
Physics Department, University of Padova and INFN, I-35131 Padova, Italy
INFN-Legnaro National Laboratories, I-35020 Legnaro(Padova), Italy
Physics Department, University of Udine and INFN, I-33100 Udine, Italy
g
General Physics Institute, University of Milano and INFN, I-20133 Milano, Italy
The EXOTIC collaboration is installing a facility for the in flight production of exotic ion beams at INFN Legnaro National Laboratories (LNL). The RIBs are produced in inverse kinematics mode via intense TANDEM/ALPI primary beams hitting a light gas target (H, d, 3 He, 4 He). The results of the optics calculation for 17 F produced by the 17 O(p,n)17 F reaction are presented. Special care has been adopted to stop, at several points perpendicular to the beam direction, the contaminants due to the primary beam. 1. INTRODUCTION In the last decade the strong scientific interest in the physics that can be investigated with radioactive ion beams (RIBs) stimulated the design and the construction of different types of first generation radioactive beam facilities. New advanced ones are now under study and their realization requires a time of the order of five to ten years. In this scenario particular interest is held by small facilities, developed in existing local laboratories, which are devoted to well defined and specialized research programs. In fact they can give access to themes of advanced experimentation at a low cost and with short completion times so covering the time gap between the design and the operation of the new large international facilities. Following the above philosophy the EXOTIC collaboration had setup a facility for the in flight production of exotic ion beams at the INFN Legnaro National Laboratories [1]. The facility design takes advantage of the already existing devices, in particular the use in connection with the PRISMA large acceptance magnetic spectrometer is planned. The ∗
On leave from National Institute for Physics and Nuclear Engineering, 76900 Magurele, Romania
0375-9474/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysa.2004.09.082
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V.Z. Maidikov et al. / Nuclear Physics A 746 (2004) 389c–392c
primary
Figure 1. EXOTIC beam line layout. The primary beam is stopped in 5.
final goal is to reach a RIB current intensity in the range of 105 particles/s with very low contaminants background. 2. EXPERIMENTAL SETUP AND BEAM OPTICS CALCULATION The basic characteristics [2] of the ion production beam line are the large secondary beam acceptance of the optics elements and a maximal suppression capability of the unwanted scattered beams (primary beam, its halos and spurious beams with same magnetic rigidity as the selected RIB). Main features of the system are: horizontal plane acceptance ∆θ = ±60 mr, vertical plane acceptance ∆φ = ±90 mr, solid angle ∆ω ∼ 20 msr, and maximum magnetic rigidity Bρ = 1 Tm. The RIBs are produced in inverse kinematic mode via intense TANDEM/ALPI primary beams hitting a light gas target (H, d, 3 He, 4 He). The gas cells can be operated at room or at liquid N2 temperatures with an operational pressure up to 1 atm. For the separator we have chosen the following configuration (see Figure 1.) : 1. Production target: - 5 cm long gas target with entrance and exit Havar windows (diameter = 12 mm); 2 and 7. Quadrupole triplets: - Magnetic field at pole tip B = 0.6 T; - Aperture radius a = 80 mm; - Magnetic field length l = 300 mm; 4. Dipole bending magnet: - Deflection angle φ = 300 ; - Reference trajectory radius ρ = 0.7 m; - Magnetic field B = 1.4 T; - Pole pieces gap h = 70 mm;
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V.Z. Maidikov et al. / Nuclear Physics A 746 (2004) 389c–392c
- Pole pieces width b = 250 mm; 6. Wien Filter: - Electric plates length l = 1 m; - Electric plates gap h = 50 mm; - Electric field E = 20 kV/cm; - Magnetic field B = 0.08 T; 8. Target location: - Intermediate cylindrical scattering chamber (50 cm diameter); - PRISMA spectrometer target point. The total length of the separator is L=8.2 m in the short variant (Scattering chamber) and L=11.1 m in the long variant (PRISMA Spectrometer). The beam optics calculation was performed using the GIOS 98 code [3] and the PSI Graphic Transport code [4]. In order to stop the beam contaminants, two sets of slits have been placed along the beam line: S1 after the first quadrupole triplet, S2 after the bending magnet. A diaphragm is also placed inside the second quadrupole triplet. The effects of these slits are described in the following and illustrated in Fig.2 and Fig.3, where
X(cm)
X(cm) 10.0 8.0
8.0 4.0 0.0 -4.0 -8.0
4.0 0.0 -4.0
-8.0 -10.0 Q1
Q2
S1
Q3
S2
BM
S2
WF
Q4
Q5
Q6
Z(m) 0.0
2.0
1.0
3.0
4.0
4.4
Z(m)
Y(cm)
Y(cm)
8.0
8.0 4.0 2.5 0.0 -2.5 -4.0 -8.0
4.0 0.0 -4.0
-8.0 Q1
Q2
Q3
S1
BM
S2
Figure 2. GIOS calculations up to the S2 slit for 17 F and 17 O. In the horizontal plane the separation between particles with different magnetic rigidities can be seen.
1.0
0.0
S2
WF
2.0
Q4
Q5
3.0
3.44
Q6
Figure 3. GIOS calculations for the beam line part between S2 and the scattering chamber. In the vertical plane the output has been modified to show the effectiveness of the S3 slit.
392c
V.Z. Maidikov et al. / Nuclear Physics A 746 (2004) 389c–392c
GIOS calculations for 17 F ions (first beam to be developed) and contaminant 17 O ions (residues of the primary beam) are shown. As input parameters we used the data from[5] for the 17 O(p,n)17 F reaction with Ebeam = 83 MeV: - Secondary beam energy (17 F9+ ) E = 63±0.6 MeV, angular spread ±2o ; - Primary beam (17 O) energy after the target E = 70±0.7 MeV, angular spread ±2o . A primary beam spot at the producing target with 5 mm(horizontal)× 2.5 mm(vertical) dimensions was considered. For a certain dispersion in energy the emittance of the primary beam can be greater than the aperture of the bending magnet and this is expected to generate background due to the scattering from the walls. In order to avoid such kind of phenomena we introduced at half distance between the first quadrupole triplet and the bending magnet the first system of slits (S1) with an opening of (±2.4 ∗ ±2.4)cm (Fig.2). At the intermediate dispersive focal point (S2 position in Fig.2) we have a horizontal momentum dispersion D=5 mm/%. In the short variant, at about 50 cm from the second quadrupole triplet exit, the focusing is quasi-achromatic due to the transformation of the spatial dispersion into the angular one. In the long variant, at about 3 m distance from the second quadrupole triplet exit, we have a variable dispersion due to secondary beam dispersion matching with the PRISMA spectrometer. At about 65 cm downstream the exit of the 30o bending magnet, the secondary 17 F beam envelope would be as large as 2.0 cm in the horizontal plane and 1.0 cm in the vertical one. In this point the envelope for the primary 17 O8+ (17 O7+ ), deflected by the bending magnet to 25o (22o ), would be about ±5.5 cm (±8.5 cm) in the horizontal plane and ±2.8 cm (±4.7 cm)in the vertical one. In this same point the horizontal separation (Fig.2) between the central trajectories of the secondary 17 F beam and the most intense 17 O7+ (17 O8+ ) primary beam will be as large as 12 cm (7 cm). Consequently this is the position where the main part of the primary beam components can be stopped by a second set of slits (S2) with an opening of (±1.25 ∗±0.75)cm. The width of both the S1 and S2 slit systems can be adjusted to tune the beam line. The Wien filter is placed between the S2 and the second quadrupole triplet. At the position of the maximal separation between the RIB and the contaminants with same magnetic rigidity a diaphragm, having a radius of 1 cm, is inserted inside the Q5 quadrupole. The real effectiveness of such a diaphragm can be easily seen in the vertical plane of Fig.3. At the second focal point position the estimated secondary beam spot size is about 1.0 cm in diameter in the short variant, and about 2.3 cm in the long variant. Commissioning of the beam line is scheduled to start in November 2003. REFERENCES 1. 2. 3. 4.
M. Sandoli et al., LNL Annual Report 2001 p.192; V.Z. Maidikov et al., LNL Annual Report 2002 p.166; c 1998 IonTech build 3.0.18; GIOS 98 U. Rohrer, PSI Graphic Transport Framework based on CERN-SLAC-FERMILAB version by L. Brown et al.: CERN-Rep. 80-04 (1980); 5. B. Harss et al., in Proceedings of the Particle Accelerator Conference, Vancouver, 1997 (IEEE, New York, 1998).
The optics of the exotic beam line at LNL V.Z. Maidikova , T. Glodariub∗ , M. La Commarac , M. Sandolic , C. Signorinid , L. Costae , F. Soramelf , R. Bonettig , A. De Rosac , M. Di Pietroc , A. Guglielmettig , G. Inglimac , B. Martinc , M. Mazzoccod , D. Pierroutsakouc , M. Romolic , P. Scopeld , and L. Stroee∗ a
Institute for Nuclear Research, National Academy of Sciences, 06380 Kiev, Ukraine
b
Physics Department, University of Padova and INFN-LNL, I-35131 Padova, Italy
c
Physics Department, University of Napoli and INFN, I-80125 Napoli, Italy
d e f
Physics Department, University of Padova and INFN, I-35131 Padova, Italy
INFN-Legnaro National Laboratories, I-35020 Legnaro(Padova), Italy
Physics Department, University of Udine and INFN, I-33100 Udine, Italy
g
General Physics Institute, University of Milano and INFN, I-20133 Milano, Italy
The EXOTIC collaboration is installing a facility for the in flight production of exotic ion beams at INFN Legnaro National Laboratories (LNL). The RIBs are produced in inverse kinematics mode via intense TANDEM/ALPI primary beams hitting a light gas target (H, d, 3 He, 4 He). The results of the optics calculation for 17 F produced by the 17 O(p,n)17 F reaction are presented. Special care has been adopted to stop, at several points perpendicular to the beam direction, the contaminants due to the primary beam. 1. INTRODUCTION In the last decade the strong scientific interest in the physics that can be investigated with radioactive ion beams (RIBs) stimulated the design and the construction of different types of first generation radioactive beam facilities. New advanced ones are now under study and their realization requires a time of the order of five to ten years. In this scenario particular interest is held by small facilities, developed in existing local laboratories, which are devoted to well defined and specialized research programs. In fact they can give access to themes of advanced experimentation at a low cost and with short completion times so covering the time gap between the design and the operation of the new large international facilities. Following the above philosophy the EXOTIC collaboration had setup a facility for the in flight production of exotic ion beams at the INFN Legnaro National Laboratories [1]. The facility design takes advantage of the already existing devices, in particular the use in connection with the PRISMA large acceptance magnetic spectrometer is planned. The ∗
On leave from National Institute for Physics and Nuclear Engineering, 76900 Magurele, Romania
0375-9474/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysa.2004.09.082
390c
V.Z. Maidikov et al. / Nuclear Physics A 746 (2004) 389c–392c
primary
Figure 1. EXOTIC beam line layout. The primary beam is stopped in 5.
final goal is to reach a RIB current intensity in the range of 105 particles/s with very low contaminants background. 2. EXPERIMENTAL SETUP AND BEAM OPTICS CALCULATION The basic characteristics [2] of the ion production beam line are the large secondary beam acceptance of the optics elements and a maximal suppression capability of the unwanted scattered beams (primary beam, its halos and spurious beams with same magnetic rigidity as the selected RIB). Main features of the system are: horizontal plane acceptance ∆θ = ±60 mr, vertical plane acceptance ∆φ = ±90 mr, solid angle ∆ω ∼ 20 msr, and maximum magnetic rigidity Bρ = 1 Tm. The RIBs are produced in inverse kinematic mode via intense TANDEM/ALPI primary beams hitting a light gas target (H, d, 3 He, 4 He). The gas cells can be operated at room or at liquid N2 temperatures with an operational pressure up to 1 atm. For the separator we have chosen the following configuration (see Figure 1.) : 1. Production target: - 5 cm long gas target with entrance and exit Havar windows (diameter = 12 mm); 2 and 7. Quadrupole triplets: - Magnetic field at pole tip B = 0.6 T; - Aperture radius a = 80 mm; - Magnetic field length l = 300 mm; 4. Dipole bending magnet: - Deflection angle φ = 300 ; - Reference trajectory radius ρ = 0.7 m; - Magnetic field B = 1.4 T; - Pole pieces gap h = 70 mm;
391c
V.Z. Maidikov et al. / Nuclear Physics A 746 (2004) 389c–392c
- Pole pieces width b = 250 mm; 6. Wien Filter: - Electric plates length l = 1 m; - Electric plates gap h = 50 mm; - Electric field E = 20 kV/cm; - Magnetic field B = 0.08 T; 8. Target location: - Intermediate cylindrical scattering chamber (50 cm diameter); - PRISMA spectrometer target point. The total length of the separator is L=8.2 m in the short variant (Scattering chamber) and L=11.1 m in the long variant (PRISMA Spectrometer). The beam optics calculation was performed using the GIOS 98 code [3] and the PSI Graphic Transport code [4]. In order to stop the beam contaminants, two sets of slits have been placed along the beam line: S1 after the first quadrupole triplet, S2 after the bending magnet. A diaphragm is also placed inside the second quadrupole triplet. The effects of these slits are described in the following and illustrated in Fig.2 and Fig.3, where
X(cm)
X(cm) 10.0 8.0
8.0 4.0 0.0 -4.0 -8.0
4.0 0.0 -4.0
-8.0 -10.0 Q1
Q2
S1
Q3
S2
BM
S2
WF
Q4
Q5
Q6
Z(m) 0.0
2.0
1.0
3.0
4.0
4.4
Z(m)
Y(cm)
Y(cm)
8.0
8.0 4.0 2.5 0.0 -2.5 -4.0 -8.0
4.0 0.0 -4.0
-8.0 Q1
Q2
Q3
S1
BM
S2
Figure 2. GIOS calculations up to the S2 slit for 17 F and 17 O. In the horizontal plane the separation between particles with different magnetic rigidities can be seen.
1.0
0.0
S2
WF
2.0
Q4
Q5
3.0
3.44
Q6
Figure 3. GIOS calculations for the beam line part between S2 and the scattering chamber. In the vertical plane the output has been modified to show the effectiveness of the S3 slit.
392c
V.Z. Maidikov et al. / Nuclear Physics A 746 (2004) 389c–392c
GIOS calculations for 17 F ions (first beam to be developed) and contaminant 17 O ions (residues of the primary beam) are shown. As input parameters we used the data from[5] for the 17 O(p,n)17 F reaction with Ebeam = 83 MeV: - Secondary beam energy (17 F9+ ) E = 63±0.6 MeV, angular spread ±2o ; - Primary beam (17 O) energy after the target E = 70±0.7 MeV, angular spread ±2o . A primary beam spot at the producing target with 5 mm(horizontal)× 2.5 mm(vertical) dimensions was considered. For a certain dispersion in energy the emittance of the primary beam can be greater than the aperture of the bending magnet and this is expected to generate background due to the scattering from the walls. In order to avoid such kind of phenomena we introduced at half distance between the first quadrupole triplet and the bending magnet the first system of slits (S1) with an opening of (±2.4 ∗ ±2.4)cm (Fig.2). At the intermediate dispersive focal point (S2 position in Fig.2) we have a horizontal momentum dispersion D=5 mm/%. In the short variant, at about 50 cm from the second quadrupole triplet exit, the focusing is quasi-achromatic due to the transformation of the spatial dispersion into the angular one. In the long variant, at about 3 m distance from the second quadrupole triplet exit, we have a variable dispersion due to secondary beam dispersion matching with the PRISMA spectrometer. At about 65 cm downstream the exit of the 30o bending magnet, the secondary 17 F beam envelope would be as large as 2.0 cm in the horizontal plane and 1.0 cm in the vertical one. In this point the envelope for the primary 17 O8+ (17 O7+ ), deflected by the bending magnet to 25o (22o ), would be about ±5.5 cm (±8.5 cm) in the horizontal plane and ±2.8 cm (±4.7 cm)in the vertical one. In this same point the horizontal separation (Fig.2) between the central trajectories of the secondary 17 F beam and the most intense 17 O7+ (17 O8+ ) primary beam will be as large as 12 cm (7 cm). Consequently this is the position where the main part of the primary beam components can be stopped by a second set of slits (S2) with an opening of (±1.25 ∗±0.75)cm. The width of both the S1 and S2 slit systems can be adjusted to tune the beam line. The Wien filter is placed between the S2 and the second quadrupole triplet. At the position of the maximal separation between the RIB and the contaminants with same magnetic rigidity a diaphragm, having a radius of 1 cm, is inserted inside the Q5 quadrupole. The real effectiveness of such a diaphragm can be easily seen in the vertical plane of Fig.3. At the second focal point position the estimated secondary beam spot size is about 1.0 cm in diameter in the short variant, and about 2.3 cm in the long variant. Commissioning of the beam line is scheduled to start in November 2003. REFERENCES 1. 2. 3. 4.
M. Sandoli et al., LNL Annual Report 2001 p.192; V.Z. Maidikov et al., LNL Annual Report 2002 p.166; c 1998 IonTech build 3.0.18; GIOS 98 U. Rohrer, PSI Graphic Transport Framework based on CERN-SLAC-FERMILAB version by L. Brown et al.: CERN-Rep. 80-04 (1980); 5. B. Harss et al., in Proceedings of the Particle Accelerator Conference, Vancouver, 1997 (IEEE, New York, 1998).