Requirements%20on%20fill-to-fill%20reproducibility

1
Requirements on fill-to-fill reproducibility

• S. Fartoukh, M. Giovannozzi

• Based on the presentation given by Stephane to
  FQWG on 26/04/2004 in the framework of the
  analysis of the RMS system
• Some additions to take into account magnets other
  than MBs and MQs

2
Introduction

• The analysis is based on relaxed requirements for
  reproducibility of magnetic field quality of LHC
  magnets
• Needs during commissioning phase.
• Needs during nominal operation split into
• Machine tuning with a pilot
• Nominal Intensity

3
Needs during commissioning - I
Multipole Requirements Criteria/assumptions
lt b1 gt 5 units with the RF off a) Small fraction ( 1sb at QF) of the available aperture b) DQ 0.07 (via MSs and 1 units of uncorrected b3 in the MBs)
lt b1 gt 2 units with the RF on a) 95 of the bunch captured to optimize BPM sensitivity. b) Tune shift. see below.
b1 random None Beam threading available
lt a1 gt and a1 random None Beam threading available
lt b2 gt in MB lt b2 gtV1 lt b2 gtV2 0.2 units DQ 0.03 (half of the effect induced by feed-down from MCS)
lt b2 gt in MQ lt b2 gt 4 units RF off DQ 0.03 (half of the effect induced by feed-down from MCS)
lt b2 gt in MQ D(B2MQ/B1MB ) 4 units RF on DQ 0.03 (half of the effect induced by feed-down from MCS)
lt a2 gt in MBs lt a2 gt known and corrected within 0.2 units per sector. c- 0.03 (included in an overall budget of 0.1, i.e just compatible with the commissioning tunes 0.285/0.385)
a2 random random a2 known in each dipole and corrected within 0.6 units r.m.s. c- 0.015 (included in an overall budget of 0.1, i.e just compatible with the com. tunes 0.285/0.385)
Some margin available Hard limit
SF, FQWG meeting 26/04/04
4
Needs during commissioning - II
Multipole Requirements Criteria/assumptions
lt b3gt in MB lt b3gt known and corrected within 1 units over the ring (correction per sector within 2 unit) a) Q 50 inducing tune spread or modulation but DA gt 6s for 1000 turns b) Coherence time after a kick of only 10 to 20 turns for sd 2-4 10-4
Other multipoles None DA gt 6s for 1000 turns without any a3/b4/b5 correction, coherence times of about 100 turns if Q corrected.
Some margin available Hard limit
SF, FQWG meeting 26/04/04
5
Needs for nominal operation tuning with pilot or
few nominal bunches - I
Multipole Requirements Criteria/assumptions Criteria/assumptions
lt b1 gt 1 units RF capture (99 of the bunch) and tune shift. RF capture (99 of the bunch) and tune shift.
lt a1 gt 1 units Vertical p-bumps reaching 0.5 mm in the arc QDs and inducing coupling c- 0.007. Vertical p-bumps reaching 0.5 mm in the arc QDs and inducing coupling c- 0.007.
b1 and a1 random 0.6 units r.m.s. a) Change of the CO and CO reaching 1 sb peak (95 c.l.) ? inj. oscillations ? 50 emittance growth (with damper off) b) From MS feed-down, DQ 0.010 and c- 0.008 a) Change of the CO and CO reaching 1 sb peak (95 c.l.) ? inj. oscillations ? 50 emittance growth (with damper off) b) From MS feed-down, DQ 0.010 and c- 0.008
lt b2 gt in MBs lt b2 gtV1 lt b2 gtV2 0.04 units DQ 0.005 ? DQ lt 0.03? 0.02 (distance to 3rd and 4th resonances) before and after first CO correction
lt b2 gt in MQs D(B2MQ/B1MB ) 2 units DQ 0.015 ? DQ lt 0.03? 0.02 (distance to 3rd and 4th resonances) before and after first CO correction
lt a2 gt in MBs lt a2 gt anticipated within 0.06 units per sector. c- 0.010 c- 0.03?0.015 before and after first CO correction, ? machine possibly fully coupled before the first CO correction.
a2 random in MBs random a2 known per dipoles and corrected within 0.2 units r.m.s. c- 0.005 (95 c.l.) c- 0.03?0.015 before and after first CO correction, ? machine possibly fully coupled before the first CO correction.
Some margin available Hard limit
SF, FQWG meeting 26/04/04
6
Needs for nominal operation tuning with pilot or
few nominal bunches - II
Multipole Requirements Criteria/assumptions
lt b3gt in MBs lt b3gt anticipated within 0.1 to 0.2 units over the ring a) Q 5 to 10 gt DA 9s ? 6s for 100000 turns. b) Coherence time 100? 50 turns (with nominal sd 4. 10-4 ).
lta3gt in MBs lta3gt anticipated within 0.3 units per sector Q 1000 (? D Q 1 for off-momentum meas. at d 10 -3 ).
ltb4gt in MBs ltb4gt anticipated within 0.04 units over the ring. Q 500 and DQ (6s) 10 3 (i.e. 50 of the overall budget)
ltb5gt in MBs lt b5gt anticipated within 0.2 units over the ring a) DA drops to 10.5s (DQ (6s, d 10 3 ) 1.5 10 -3) b) Q 10 106 starts to degrade the Q measurement accuracy.
Some margin available Hard limit
SF, FQWG meeting 26/04/04
7
Demands for nominal operation - I
Criteria Tolerance on beam observable Tolerance on multipole correction accuracy
RF capture injected batches only ? ltlt ?bucket 10-3 Residual lt b1 gt (much) less than 1 units
Collimation efficiency all operation modes Essentially CO variation lt 0.2s (dynamic beta-beat less demanding and in any case not easily correctable) Random b1 and a1 less than 0.1 units r.m.s.
Tune control all operation modes DQ 3. 10 3 ? 10 3 in collision a) D(B2MQ/B1MB ) lt 0.25 units (during decay /snap-back/ramp corresponding to DQ 2. 10 3 ) b) lt b2 gtV1 lt b2 gtV2 lt 0.01 units
Coupling control all operation modes Dc- 3. 10 3 ? 10 3 in collision Residual lt a2 gt per sector less than 0.03 units ? 0.01 units
Chromaticity control all operation modes DQ 1 ? 3 in collision (at 450GeV, the tolerance may be relaxed prop. to the beam intensity, but not exceeding 5 units for DA preservation) lt b3 gt over the ring corrected via MSs and/or MCSs within 0.02 to 0.06 units
SF, FQWG meeting 26/04/04
8
Demands for nominal operation - II
Criteria Tolerance on beam observable Tolerance on multipole correction accuracy
Detuning control injection/decay/snap-back DQ (6s) lt 2. 10 3 out of which the incompressible MQ contribution of 10 3 must be subtracted lt b4 gt corrected via MOs within 0.04 units (gt Q 500)
DA preservation essentially at 450 Gev DA11.5 0.5 s (taking into account the above requirements concerning multipoles other than b5). lt b5 gt corrected via MCDs within 0.1 units over the ring and 0.2 units per sector
Variation of Q(? ) during off momentum measurement mainly for 450 Gev Q lt 1000 (taking into account the above constraint on b4) and Q lt 0.5 106 lta3gt corrected via MSSs within 0.2 units per sector lt b5 gt corrected via MCDs within 0.1 units over the ring
SF, FQWG meeting 26/04/04
9
Summary for MBs and MQs
Multipole MBs MBs MBs MQs MQs
Comm. Nominal (setting-up) Nominal Comm. Nominal
lt b1 gt 2 - 5 1 ltlt 1
b1 random None 0.6 lt 0.1
lt a1 gt None 1
a1 random None 0.6 lt 0.1
lt b2 gt 0.2 0.04 0.01 4 2
lt a2 gt 0.2 0.06 0.01
a2 random 0.6 0.2
lt b3 gt 1 0.1- 0.2 0.02- 0.06
lt a3 gt 0.3 0.2
lt b4 gt 0.04 0.04
lt b5 gt 0.2 0.1
Figures are in units. Limits for random
components are expressed in rms.
10
Summary for other magnets
Magnets Transfer function Transfer function Harmonics Harmonics
Comm. Nominal Comm. Nominal
MBXW 2 - 5 1 - -
MBX 2 - 5 1 1 0.2
MBRC 2 - 5 1 1 0.2
MBRS 2 - 5 1 1 0.5
MBW 2 - 5 1 - -
MBRB 2 - 5 1 1 0.5
MQM-like 10 5 1 0.5
MQY 10 5 1 0.5
MQTLH 10 5 1 0.5
MQTLI 10 5 1 0.5
MQWA/B 10 5 1 1
MQX 5 2 1 0.2
Relevant harmonics b3, b5
Relevant harmonics b6
Relevant harmonics b3, b6
MO crucial to have zero field at injection!
Some margin available Hard limit