Progress ofbunch compressor simulations
for PITZ
Transparencies presented by A.Oppelt
at the LAOLA-Workshop in Wismar
8.6.2012
Running ASTRA with more longitudinal bins compared to the results presented end Nov. 2011 → no visible differences
1. Update of ASTRA simulations
Longitudinal phase space at z = 5 m(Gun +10 deg / Booster +40 deg)
40 bins 280 bins
2. Slight modification of the dogleg design
Use first approach BC layout with some changes
• dogleg with compression factor C = 4 (from RB)• R56 = (-)0.044 (from C and momentum chirp)
and some other BC parameters adjusted
D1
D2
Q1
Q2
Q3
S1
S2
L=1m
• use optimized dogleg setup from Nov. 2011 (with the problem of unrealistic quad settings)
• use ASTRA particle distribution as inputfor elegant tracking
• no re-optimization of quad settings• no matching into dogleg applied yet
3. Elegant simulation results
Longitudinal phase space distributions(elegant tracking results) in the dogleg and at the end of the dogleg
@ dogleg entrance (elegant input generated from ASTRA output):
3. Elegant simulation results (ctd.)
Conclusion from the elegant tracking results:• first simulation of dogleg was performed with elegant• bunch compression works• non-uniform compression of the bunchlets due to slightly non-linear chirp
at dogleg entrance
Remaining issues and possible solutions1. re-optimize dogleg layout (dipole parameters, drift lengthes) → open2. reduce compression in dogleg to 50% and apply two of them → open
(setup can be used as ‘normal D-shape chicane’ when switching off the quads)3. run ASTRA for 5 different single beamlets (to be combined later) → done4. optimize dogleg for each beamlet seperately (cross-check dogleg capability) → open5. invert chirp of the bunch by choosing inverse accelerating phases
and try to use a normal D-shape chicane (4 dipoles) → done
1st bunchlet: 10 pC (40 long. bins)
Comparison of long. phase spaces at z=5m (after booster, start of matching section)
Autophasing vs. fixed phase(relative to on-crest phase) (defined by optimum phase(Gun +10 deg, Booster +40 deg) of 5 bunchlet pulses)
→ only small differences in chirp, energy spread, …
4. Single bunchlet ASTRA simulation results
5th bunchlet (probe pulse): 10 pC (280 long. bins)
4. Single bunchlet ASTRA simulation results (ctd.)
Idea of RB: use inverted chirp and compress bunch in D-shape chicane (4 dipoles)
Problem: space charge destroys bunchlet structure already in the gun
5. Bunch compression in a chicane
Longitudinal phase space at z = 3 m (booster entrance) from ASTRA
Gun +10 deg Gun -10 deg
→ chirp generation has to happen in the boosterBut: non-linear phase space will induce problems during the compression
→ to test: on-crest acceleration in the gun
Longitudinal phase space at z = 5 m from ASTRA
Gun +10 deg Gun + 10 deg Gun -10 degBooster +40 deg Booster -40 deg Booster -40 deg
5. Bunch compression in a chicane (ctd.)
Design of the 4-dipole D-shape chicane: R56 = 0.058, α=76.5 deg, …
5. Bunch compression in a chicane (ctd.)
Conclusion from the elegant tracking results:• very first parameter setup realized and
tracking with elegant performed• bunch compression works• non-uniform compression of the bunchlets due to
non-linear chirp at chicane entrance
6. Elegant simulation results
Longitudinal phase space distributions(elegant tracking results) in the chicane and at the end of the chicane
@ chicane entrance (elegant input generated from ASTRA output):