1. A beam dynamics tolerance study of the CLIC-CRAB cavity
Dr Ian Shinton The University of Manchester; Cockcroft Institute, Daresbury, UK

2. Manchester beam dynamic CLIC CRAB work program
1) Basic tolerance calculations of the CRAB cavity using the special edition of the PLACET beam tracking code and Guinea-pig
2) Long range wakefield study of the CLIC crab cavity using the special edition of the PLACET beam tracking code
3) Tolerance study using beam off-sets for the CLIC CRAB cavity using the special edition of the PLACET beam tracking code and Guinea-pig.
4) Short range wakefield study of the CLIC crab cavity using the special edition of the PLACET beam tracking code 2

3. Operating voltage for the CLIC-CRAB calculated from PLACET
SET: ELECTRON LINE PHASE = POSITRON LINE PHASE=0
N_slice=101
N=101
Total particles=10201
Voltage
MaxV=2.584MV
Lum=2.5205e34
98% Lum
2.4930<V<2.6710

4. Differential Phase range for the CLIC-CRAB calculated from PLACET
SET POSITRON LINE PHASE=0
V=Vmax=2.584MV
Differential Phase
N_slice=101
N=101
Total particles=10201
MaxPhase=0deg
Lum=2.5198e34
98% Lum
<Phase<0.0220

5. Differential Roll range for the CLIC-CRAB calculated from PLACET
Very sensitive to roll tolerance

6. CRAB Cavity issue
We notice a discrepancy between a simulation in which we have a crossing angle and the crab cavities switched on as compared to a perfectly striaght linac calculation
There are some geometric effects in the phase space plots…..
Both simulations should give the same result – however there is a discrepancy in the luminousity of ~10% between the results
We think this may be an effect of the sextupoles near the IP
Things to resolve issue as previously sugested by various people/groups
Swap the drift tubes and crab cavities around
Use of an anti-crab cavity to correct roll tolerance issues
Redesign of magnets 6

8. There is a 10% loss in luminousity with the CRAB cavity as compared to without…

10. Comparison of CLIC-CRAB calculated from PLACET for:
Swapping D020 drift space and CLIC-CRAB cavity 10

11. Previous Result with D020 then Crab
Operating voltage for the CLIC-CRAB calculated from PLACET
SET: ELECTRON LINE PHASE = POSITRON LINE PHASE=0
N_slice=101
N=101
Total particles=10201
Voltage
MaxV=2.584MV
Lum=2.5205e34
98% Lum
2.4930<V<2.6710 11

12. GARCIA – swap D020 drift space and Crab voltage scan
i.e. Crab then D020
SET: ELECTRON LINE PHASE = POSITRON LINE PHASE=0
N_slice=101
N=101
Total particles=10201
Voltage
MaxV=2.548MV
Lum=2.5451e34 12

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15. 15

16. What does this tell us
Swapping of the drift-tubes and Crab cavities makes no difference to the calculation…which is good (since this is what we expect)
So these effects are potentially real effects and may be geometric in nature. 16

17. Comparison of CLIC-CRAB calculated from PLACET for:
Putting an energy spread of 0 and replacing the sextupoles with drift spaces 17

18. Lets remove the no linear effects of the sextupoles and see what happens…
The sextupoles correct for cromotisity effect, however they may also have an adverse effect on the beam due to the “crabbing effect” from the crab cavities.
If we put a 0 energy spread and replace the sextupoles (in the CLIC BDS deck) with drift spaces, then we should obtain the same results for both cases (straight beam line and a beamline with a crossing angle and crab cavities). 18

19. Now we obtain the same results for all terms for both cases (i. e
Now we obtain the same results for all terms for both cases (i.e. all phase space plots are now the same)
However there are still some non-linear effects….

20. This looks like an effect from a decapole magnet – DD0 in the deck
However there are still some non-linear effects….
This looks like an effect from a decapole magnet – DD0 in the deck