Tools for Luminosity Optimisation in the LHC
2-day mini workshop held at CERN
on the 15th & 16th April 1999
  
 
 
Contents:
 
  Agenda
  List of Participants
  Presentations
  Summary
 
 
Click here to download a pdf version of the workshop proceedings
 (Printed copies can be obtained on request from Madeleine Catin)
 
 
Agenda:

1st Day:
 
Topic Speaker Time
Start of Workshop 10:00h    
Purpose of this workshop H.Schmickler 10’
Absolute Luminosity Calibration (TOTEM)

Principle, Running scenarios over the years, 

 W.Kienzle 15’
Procedures for initial collision steering,

Procedures for L-optimisation,

Expectations for L-Imbalance within the batches, expectations for L-Imbalance between IPs, Requirements for Instrumentation

 B.Jeanneret 30’
Experience with L-Optimisation at the ISR K.Potter 10’
Experience from PETRA, LEP and SPS R.Schmidt 15’
Experience from PEP-II W.Kozanecki 15’
Lunch Break until 14:00h    
Inventory of already planned LHC instruments

(Emittance, BCT, BPMs) and their diagnostics potential

 C.Bovet  30’
The proposed SEM L-monitor  S.Weisz 20’
The proposed TAS and TAN instrumentation B.Turner 15’
Coffee break    
Hardware layout of TAS and TAN inst. P.Datte 15’
Cold silicon detectors as technological alternative V.Palmiery, T.Niinikoski 20’
Implication of the above proposals for the LHC layout C.Fischer 15’
Agenda of 2nd day (discussions, conclusions) will be established during 1st day

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Participants:

Chairman: Hermann Schmickler (SL/BI)

Secretary: Rhodri Jones (SL/BI)

 

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Presentations:
 
      Introduction
 H. Schmickler View  
      Absolute Luminosity Calibration (TOTEM)
 W. Kienzle  [see CERN/LHCC 99-7]  
      Luminosity Stability and control at the LHC
 B. Jeanneret View  
      Experience from the ISR
 K. Potter View  
      Experience from PETRA, LEP and SPS
 R. Schmidt View  
      Experience from PEP-II
 W. Kozanecki View  
      LHC Instruments
 C. Bovet View  
      The Proposed SEM L-monitor 
 S. Weisz View  
      The Proposed TAS and TAN Instrumentation
 B. Turner View  
      Cold Silicon Detectors
 V. Palmieri View  
      Cold Silicon Detectors - Summary
 T. Niinikoski View  
      Implication of the TAN for the LHC layout
 C. Fischer View  
      Summing Up
 H. Schmickler View  
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Summary:
 
Absolute Luminosity Measurements with d L/L < 2% is the task of the LHC experiments
   
Absolute Luminosity Measurements with d L/L ~ 5% for luminosities above 1030 cm-2s-1 via a machine L-monitor and occasional cross calibrations to the LHC experiments is the task of the machine community.
   
Requirements for the Luminosity Monitor:
  1)  Available in all 4 IPs.
  2) Sensitivity of Luminosity reading to variations of IP position (x*,y* < 1mm) and angle at IP (x*',y*' < 10 m rad ?) has to be lower than 1%.
  3) The dynamic range with "reasonable" acquisition times for 1% precision has to cover 1028 cm-2s-1 to 1034 cm-2s-1 .
  4)  In order to see structure along the batches, a minimum bandwidth of 132 kHz is required. For the lower 2 decades of the dynamic range the bandwidth can be much lower since the machine will operate using only 36 bunches.
   
Concerning the two (three) presented proposals:
  1) The SEM monitor will be difficult to make operational in the requested dynamic range of 106. It is of no interest to the machine due to the severe bandwidth limitation (~ 1kHz). The technological alternative of cold silicon counters should be tried instead and studied rather rapidly.
  2) The proposal of a scintillator hodoscope needs much more study. However, if the studies on cold silicon counters prove to be promising, then the scintillator proposal should not be followed up.
  3) The LBL proposal with the comments below is supported by CERN and in particular by the SL beam instrumentation group. 
This means that the requested studies should be carried out, with beam tests performed over the next two years. 
   
Items to be reviewed on the LBL proposal:
  1) Simulations should be performed to investigate the collimation effect of D1 on the TAS and TAN detectors when the position of the IP changes.
  2) The position of the TAN should be reviewed with the aim of moving it 5m closer to IP. This would allow for the optimisation of the light path of Synchrotron Light Monitor.
  3) Space should be reserved for instrumenting the TAS. The final decision of whether to go ahead will be taken in 2002. It should be noted that only by instrumenting both the TAN and TAS would it become possible to measure the absolute position of the IP.
  5) The front end electronics and acquisition system should be reviewed, taking into account the following points:
  • The detector should be made independent of external machine timing.
  • The requirement of a large dynamic range is more important than a high bandwidth. The possibility of using a lower bandwidth for the lower 2 decades of the dynamic range should be investigated, since the machine will operate at such luminosities using only 36 bunches.
  • The running scenario for the detector is up to 20 years without access in a highly radioactive zone. Any mechanical design, which weakens the detector, has to be avoided. Hence if operation at 40MHz is pursued then the subsequent design of the detector should not compromise its reliability.
 

The situation will be reviewed in spring 2002. By this time it is expected that the LBL group will have completed its prototype testing of the TAN monitor. At the same time the scintillator or cold silicon detector proposal will also be reviewed, allowing a final decision on the LHC luminosity monitor to be made.

 

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Rhodri Jones (SL/BI)
26/4/1999