Lattice optimization for low charge Lattice optimization for low charge state heavy ion operation state heavy ion operation state heavy ion operation state heavy ion operation Collimation concepts for beam ions Collimation concepts for beam ions after a charge change after a charge change CERN Collimator Workshop 3rd-5th Sep. 2007 Jens Stadlmann, FAIR Synchrotrons
Contents Contents • Motivation: Heavy ions of intermediate charge states for the FAIR project at the GSI FAIR project at the GSI • Benchmarking of different lattice concepts for SIS100 • Conclusion Conclusion 3rd-5th September J. Stadlmann
The Future Accelerator Facility - FAIR SIS 100/300 SIS18 UNILAC HESR Gain Factors Super FRS � Primary beam intensiy : x 100 – 1000 CR � Secondary beam intensiy : x 10000 � Ion energy : x 15 Ion energy : x 15 � New: cooled pbar beams (15 GeV) NESR � Special : intense cooled RIBs � Parallel operation and time sharing p g 3rd-5th September J. Stadlmann
Motivation: Beam Life Time in FAIR Synchrotrons High intensity, heavy ion beams require intermediate charge states High intensity heavy ion beams require intermediate charge states Dynamic Pressure Static Pressure � Life Time of U 28+ is � Desorption Processes degenerate significantly shorter than of U 73+ the residual gas pressure the residual gas pressure � Life Time of U 28+ depends � Beam losses increase with strongly on the residual gas strongly on the residual gas number of injected ions number of injected ions (vacuum instability) pressure and gas components 3rd-5th September J. Stadlmann
Residual Gas Pressure Dynamics Fast variations (time scale ms) Fast variations (time scale ms) Slow variations (time scale s - h) Slow variations (time scale s h) up to two orders of magnitude 3rd-5th September J. Stadlmann
Main Issue: Vacuum Stabilization � Short cycle time and short sequences SIS18: 10 T/s - SIS100: 4 T/s (high pulse power > new network connection) � High pumping power, optimized XHV spectrum SIS18: NEG coating (local and distributed) g ( ) increased SIS100: Actively cooled magnet chambers 4.5 K pressure � Localization of losses and control ion beam of desorption gases wedge collimator SIS18/SIS100: Desoprtion Scrapers SIS100: Optimized lattice structure � Low-desorption rate materials D Desorption rate and ERDA measurements ti t d ERDA t � Minimization of systematic (inital) losses 3rd-5th September J. Stadlmann
Initial loss mechanisms Initial loss mechanisms 3rd-5th September J. Stadlmann
Special lattice layout to control the dynamic vaccum Special lattice layout to control the dynamic vaccum Basic principles p p • The ions should not be lost at arbitrary positions. Peaked ! • The losses should be peaked in sections with The losses should be peaked in sections with sufficient space for a dedicated scraper system • The scrapers should not reduce the acceptance. • The circulating beam and the contaminants should be clearly separated at the positions of the Separated! scrapers which requires a waist in the beam envelope and dispersive elements upstream. • Ideally all unwanted ions which are produced in the downstream section after one scraper should be downstream section after one scraper should be Acceptance! able to be transported at least to the next collimator. (High tune or increased aperture) 3rd-5th September J. Stadlmann
New Lattice Design Concept for U 28+ 1. From all loss mechanisms, only charge change by o a oss ec a s s, o y c a ge c a ge by collisions with the residual gas atoms leads to loss within one lattice cell ! Each lattice cell is designed as a charge separator The stripped“ beam ions (U 29+ ) 2 2. Each lattice cell is designed as a charge separator. The „stripped beam ions (U ) are well separated from the reference beam. (The low dispersion function in the SIS100 arcs complicate this issue.) 3 3. The main lattice structure optimization criteria is the catching efficiency for U 29+ -ions The main lattice structure optimization criteria is the catching efficiency for U ions. The catching efficiency for U 29 - ions must be close to 100%. 4. 5. The 100 % catching efficiency must be achieved with scrapers at maximum % ff distance from the beam edge. No acceptance reduction is caused by the catcher system. 6. The ionization beam losses on cold and NEG coated surfaces shall be minimized. Minimum additional load for the UHV and the cryogenic system. Minimum additional load for the UHV and the cryogenic system. 3rd-5th September J. Stadlmann
Comparison of Scraper Efficiency η coll = N coll /N total at injection energy at injection energy High charge scraping effcienc High charge scraping effciency was as reached by lattice (cell) optimization. Many lattice structures have been compared compared. Strahlsim -> Talk by C. Omet 3rd-5th September J. Stadlmann
SIS 100 Design I: Lattice Choice and Optimization Comparison of scraper efficiency of all studied lattices Comparison of scraper efficiency of all studied lattices Vergleich alle Lattices 100% CDR (TR_DFD_4Dipole3.0Grad2.0T_08_Ausgelagert) TR_DFD_3Dipole2.9Grad2.0T_09 TR_DFD_3Dipole3.0Grad2.0T_09_Aus TR DFD 3Dipole3.0Grad2.0T 10 Ausgelagert TR_DFD_3Dipole3.0Grad2.0T_10_Ausgelagert 95% 95% TR_FDF_3Dipole2.9Grad2.0T_09 TR_FDF_3Dipole3.0Grad2.0T_09_Ausgelagert TR_FDF_3Dipole3.0Grad2.0T_10_Ausgelagert DOFO_2Dipole3.0Grad2.0T_17 90% DP_DF_2Dipole3.0Grad2.0T_13_Tune DP_DF_2Dipole3.0Grad2.0T_13_Ausgelagert DP_DF_2Dipole3.0Grad2.0T_13_Aus_Tune DP_DF_2Dipole3.0Grad2.0T_14 DP_DF_2Dipole3.0Grad2.0T_14_Tune 85% DP_DF_2Dipole3.0Grad2.0T_14_Ausgelagert DP DF 2Di l 3 0G d2 0T 14 A l t DP_DF_2Dipole3.0Grad2.0T_14_Aus_Tune limationseffizienz DP_DF_2Dipole3.0Grad2.0T_15 DP_DF_2Dipole3.0Grad2.0T_15_Ausgelagert 80% DP_DF_2Dipole3.0Grad2.0T_15_Aus_Tune DP_DF_2Dipole3.0Grad2.0T_15_Aus_T2 DP_DF_2Dipole3.3Grad1.9T_13_Ausgelagert DP_DF_2Dipole3.3Grad2.0T_13 75% DP_DF_2Dipole3.3Grad2.0T_13_Ausgelagert DP DF 2Dipole3.3Grad2.0T 14 _ _ p _ Koll DP_DF_2Dipole3.3Grad2.0T_14_Ausgelagert DP_DF_3Dipole2.7Grad2.0T_11_Ausgelagert DP_DF_3Dipole2.9Grad2.0T_11 70% DP_DF_3Dipole2.9Grad2.0T_12 DP_DF_3Dipole3.0Grad1.9T_11_Ausgelagert DP_DF_3Dipole3.0Grad2.0T_11_Ausgelagert DP_DF_3Dipole3.0Grad2.0T_12_Ausgelagert 65% DP_DF_3Dipole3.3Grad2.0T_11 DP_DF_3Dipole3.3Grad2.0T_12 DP_FD_2Dipole3.0Grad2.0T_15 DP FD 2Dipole3 0Grad2 0T 15 DP_DF_2Dipole3.0Grad2.0T_16_Aus_11/2_Tune 60% DP_DF_2Dipole3.0Grad2.0T_16_Aus_11/2 DP_DF_2Dipole3.0Grad2.0T_16_Aus_11/2_19_17 DP_DF_2Dipole3.0Grad2.0T_16_Aus_11/2_28_16 DP_DF_2Dipole3.0Grad2.0T_16_Aus_11/2_28_20 55% 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 Abstand von Strahlachse / n*R(k v Verteilung) Abstand von Strahlachse / n*R(k-v-Verteilung) 3rd-5th September J. Stadlmann
SIS100 design II, the chosen structure SIS100 design II, the chosen structure DF doublet lattice good A waist after the dispersive elements. 3rd-5th September J. Stadlmann
SIS100 design III SIS100 design III Problematic: FODO structure good g bad bad One half cell is ok, next one is bad. 3rd-5th September J. Stadlmann
SIS100 design IV SIS100 design IV Not optimal: triplet structure good bad Would work, if all dispersive elements are in the first half of the cell the first half of the cell. 3rd-5th September J. Stadlmann
SIS100 design V: Special lattice SIS100 design V: Special lattice Results and influence of better transmission The doublet structure with high The doublet structure with high momentum acceptance delivers best results. An unwanted particle just missing one collimator is "stored" missing one collimator is stored and can be collimated later. Comparison Lattices Structures for SIS100 100,0% CDR (Triplett) ciency 97,5% FODO Dublett 95,0% mation effic Speichermode Dublett Speichermode Dublett 92,5% 90,0% collim 87,5% 85,0% 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 2,1 distance from beam edge [x/beam radius] 3rd-5th September J. Stadlmann
Problem 1: Multiple Ionisation Problem 1: Multiple Ionisation p Ave SIS18 LEAR erage num R. Olsen et.al., HIF04 R Olsen et al HIF04 experimental P = 3.67x10 -11 P = 2.87x10 -11 SIS18 injection energy SIS100 injection energy SIS100 injection energy H 2 – 81.87 % 8 8 % H 2 – 83.18 % 83 8 % mber of p 2 2 CH 4 – 11.86 % He – 2.36 % CO – 3.02 % CH 4 – 10.38 % Ar – 3.25 % CO – 1.73 % N 2 – 1.38 % proj. loss Ar Ar – 0.97 % 0 97 % electrons s A. Smolyakov E [MeV/u] M lti l Multiple ionization reduces the scraping efficiency i i ti d th i ffi i Cross section interpolation The total number of multiple ionized particles is low 3rd-5th September J. Stadlmann
Problem 2: Different working points The scraping efficiency depends slightly on the tune. 3rd-5th September J. Stadlmann
Problem 3: Behaviour of lighter ions � The scraper system is optimized for heavy ions. � Lighter ions miss the scraper and are dumped in the beam pipe. � The loss rate of light ions is low, since the cross sections are lower (will be calculated). 3rd-5th September J. Stadlmann
SIS100 scraper position 80. 8 [mm] -x[mm].. +x[ -80. path length [mm] Envelopes at maximum acceptance show the position of the cathersnot interacting with the stored beam. 3rd-5th September J. Stadlmann
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