Feedback on phase adjustment with BPTX

• Using scope and LHCb BPIM boards to readout BPTX signal

• BPIM only used for triggering, phase measurements (BPTX1-BC1, BPTX2-BC1, …) done with scope

• No data recording implemented, only scope screenshots

First cogging with two beams

Beam-1 bucket 1

Beam-2 bucket 8911 Without cable+TOF estimated delay correction126.678 ns

-> Measured Vertex Z = -1.3 cm

23 Nov 2009

Vertex Z vs DT• BPTX cable length know with accuracy ~ ± 200 ps• Measured vertex Z used to x-check/calibrate DT offset, corrected value: 126.820

nsBPTX-1 – IP2 = 146085.5 mmBPTX-2 – IP2 = 145361.5 mm(DTOF = 2.922 ns)

BPTX-1 cable delay = 800.4 nsBPTX-2 cable delay = 670.8 ns

Estimated offsetDT(B1-B2)= 126.678 ns

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4-4

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LAS

Final resolution:~ 50 ps (tbc!)

Vertex Z variations

895 900 905 910 915 920 925-3.5

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ex Z

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RF problems

Phase adjust

To be checked

Large changes related to RF phase adjust, some ~ 50-100 ps variations to be understood

More feedback

• DT with multibunching: nothing special implemented in 2009

• Tolerable beam spot shift: < 1cm within same fill (run), also depending on beam longitudinal size (to be confirmed…). Larger shifts clearly an issue if during same fill/run

• External clock handshake? Resynchro only during setup, change needs agreement on new procedure

2010 issues

• No synchronized BCref for 2010: in principle not an issue

• Will we use the BPTX to check the alignment? Should/could the data be published? Which format? LHCb BPIM (with new FW) will measure bunch by bunch phase and intensity + DT of bunch pairs, check filling scheme (ghost bunches, abort gap), data published over DIP (agreed format)

2010 issues

• If the phase is 'wrong', what should be the procedure? (experts won't be there night and day on a long term basis) Procedure to be agreed with experiments

• If rephasing is done, could it be during 'stable beam'? If yes, will the feedback be given by vertex reconstruction? How fast is it? Not during ‘stable beam’ unless new procedure is established. Info on vertex available ‘online’.