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LHC Intensity measurement (emphasis on Fast BCTs)
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Europe/Zurich
866/1-A04 (CERN)
Jean-Jacques:
3 promilles difference between FBCTs_VFC and DCCTs on 4th of September
Measured between 3 and 4GeV
FBCT B1 now off with 4%. Action David
System A: 7.5E6 p/bin since 10/7, very stable, except 5 points which are very different.
To be understood because system A has not been touched. Action Jiri
B1 Best noise performance. FR DAB two times better than FR-VFC
DAB measurement averaged over 1s while the VFC data 50Hz, so a factor 7 can be gained. Action Stephane
B1 BtB vs BQM today very goo agreement, much better than 1%
Calibration with DCCT stable since Juli
Open questions:
Can we improve noise by averaging: Yes action Stephane
How do we plan to calibrate: For the moment we will stay with DCCT calibration!
How is gain selection working?
Do we plan to have a check in the sequencer?:
Did we assess the ADC linearity: Yes with DC, difficult to do precisely with pulses
What about multi turn acquisition?: Stephane will implement turn by turn acquisition triggered by intensity changes (injection or dump)
What about capture ???
What about BCTFD: 2 VME crates for VFC_DI will be installed in TS3. Rolling acquisition buffer stopped by kicker signal.
Which monitor do we chose in the end.:
JJ propose to organise a MD to assess:
Phase scan: Will be checked by David and Jiri
Position scan: Done by Michal. He will send MD notes to JJ
Mix of intensities: MD to be planned in October: David, Jiri
Michal: BCTW calibration
High frequncy cutoff of calibration winding: 1MHz
Disconnected for the moment, due to ground loops
Beam coupling to calibration winding minimised
Long pulse 350 us, very stable, only amplitude calibration used
Use same generator to all BCTW using switch, 1A current
Some ringing the first 5us observed
50 ppm accuracy after 50us
5ppm standard deviation over 24h.
1A = 90% vof HG and 8 % of LG.
Not possible to increase current by a factor 10 for the LG
Should include BCTW in loop and measure droop, Action Michal
For the moment we will stay with DCCT calibration! As from discussion during JJ’s presentation.
JIRI:
SPS and LHC firmware development finished
SPS: Automatic tracking during acceleration works
di/dt andBLM included in main firmware
VME stable since June
Beam 2 system B start re-commisioning after TS2, with new amplifiers
Longterm noise averaging shows low frequency noise oscillations on all BCTs
Could be same spikes as on BCCM
B1 A DAB 2 times less noisy than VFC
Stephane:
Notes by L. Soby
The FESA server is available however to minimize the work for the different users and their application, the communication interface will be made the same as for the DAB server.
After discussion the points to be modified in the VFC FESA SW:
- averaging sumsum 50 values
- scaling factor to be set
- test and migration to 64bit
- interface for OP (fesa properties)
- turn by turn acquisition triggered by intensity changes (injection or dump)
- post-mortem and xpoc
- only system A for operation
BI intensity data:
JJ proposes to use the same mechanism used for the lifetime (not yet validated) via a FESA server as a concentrator. This server will have an interface that will not be changed and only the links with the different BCT servers will be set by BI.
Stephane will ask CO whether it is possible to define virtual devices visible as FESA devices. These devices could be configured by OP in the database.
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