Results from RF cogging sessions on Nov 20 to 23

A. Di Mauro, M. Krivda

Some basic numbers

Master RF = 400.788766 MHz1 bucket = 2.4950799 ns1 bunch = 10 buckets1 ORBIT = 35640 bucketsRevolution period 88.92464815 s

BPTX-A – IP2 = 145996.5 mmBPTX-C – IP2 = 145286.5 mm(TOF = 2.37 ns)

BPTX-A cable delay = 800.4 ± 0.1 ns (i.e. 196.76 ± 0.03 m with Vp=0.82*c)BPTX-C cable delay = 670.8 ± 0.1 ns(i.e. 164.89 ± 0.03 m with Vp=0.82*c)

BPTX-A (on beam-1)

BPTX-C (on beam-2)

FOR BUNCHES CROSSING IN IP2 BPTX-C ARRIVES 127.23 ns BEFORE BPTX-A

Cogging with BPTX• Bucket 1 is defined as the 1st after the 3 s empty

abort gap (from 34442 to 35640)• Bunches in bucket 1 of the two beams collide in IP1

and IP5• By delaying the beam 2 injection bucket by ¼ turn

the IP is displaced by 1 octant (e.g., beam-1 bucket 1 collides with beam-2 bucket 8911 in IP2)

• Cogging strategy: fix beam-1, adjust position of beam-2 bucket 1 so that buckets 1 collide in IP1/5 ->T = 0 in IP1/5, T= 66.693453 us in IP2

Cogging with BPTX

• Two scopes installed close to rack C20 (where BPTX signals are fed to BPIM – Beam Phase and Intensity Monitor – boards), in front of CTP rack

ORB1BC1ORB2BC2ORB from TTC MAIN

ORB from TTC MAINBC from TTC MAINBPTX-ABPTX-C

First measurement with single beam

BPTX1-ORB1 = 7.89646 usBPTX2-ORB2 = 42.17682 usORB2-ORB1 = 2.573 usT = (BPTX2-ORB2) + (ORB2-ORB1) – (BPTX1-ORB1)

T - 66.93453 = -29.840092 us -> IP rotated anticlockwise by ~ 1/6 orbit wrt IP1/5

Second try with single beam

BPTX1-ORB1 = 7.89646 usBPTX2-ORB1 = 74.5914128 usT - 66.93453 = 0.0015 us

Beam-2 rotated clockwise by 29.84115 us

…and finally with both beams

Beam-1 bucket 1

Beam-1 bucket 1

…and finally with both beamsFine tuning for ATLAS/CMS, ~ 1 ns correction

…and finally with both beamsFine tuning for ATLAS/CMS, 1 ns correction

..and in ALICE

Beam-1 bucket 1

Beam-2 bucket 8911 Without cable/TOF delay correction

..and in ALICE

Beam-1 bucket 1

Beam-2 bucket 8911

With 127.23 ns cable/TOF delay correction

<- Measured also by CMS