Luminosity Monitor UKNF Meeting 7 June 2010 Paul Soler, David Forrest Danielle MacLennan

2 Purpose of Luminosity Monitors  Luminosity monitor to determine particle rate close to target and extract protons on target as function of depth – independent of beam loss monitors.  Luminosity monitor will record the number of particles crossing 4 scintillators for every spill – can build up high statistics to validate particle production in target.  By having a small plastic filter we can also reduce low energy protons – some sensitivity to proton energy.  Can be used to compare particle rates close to target (luminosity monitor measures mainly protons and pions) with other counters along beamline (GVA1, TOF0, CKOV, TOF1 and FBPM counters which measure pions, muons, electrons) – validate beamline simulations  For this reason, the luminosity monitor will be very useful for beam commissioning

3  Final design of luminosity monitor: Luminosity Monitor Design Beam Cuts off: protons ~500 MeV/c pions ~150 MeV/c (6 mm thick)‏

4  Final design of luminosity monitor: Luminosity Monitor Design Beam Cuts off: protons ~500 MeV/c pions ~150 MeV/c

5  PMTs: Hamamatsu H5783P — 0.8 ns rise time — ~1x10 6 gain — Only need to provide <15V to power PMT  Readout: use NIM coincidence units and count three channels using VME scalers already in DAQ Photomultipliers 50 mm High rate capability with 20 ns coincidence gate If rate still an issue, can make more shielding LMC-12 LMC-34 LMC-1234 Discriminator set at 500 mV for all channels

6 Installation of Luminosity Monitors  Installation of Luminosity Monitor: January 2010  Many thanks to Willy, Jeff Barber, Daresbury cabling team  Installed RG58 cables (8 x 80 m between ISIS vault and MICE control room)‏  Stand modified for luminosity monitor and installed in vault

7 Installation of Luminosity Monitors  Position of luminosity monitor:10 m from target at 25 o.

8 Commissioning Luminosity Monitors  Commissioning was performed in January and 7 February with a dedicated MICE run  Purpose: define detector HV conditions, determine discriminator levels, synchronise with ISIS signals, set-up scalers, run at different beam loss levels to test correlation with LM detectors.  Unfortunately, one PMT was dead when installed in January so this also had to be replaced on 7 Feb  Gate initially 5 ms but now gate is 3.23 ms (same as trigger)‏

9 Commissioning Luminosity Monitors  Runs performed 7 February (many thanks to Terry, Pierrick, Adam and Vassil for help during shift!)‏ ActuationsRun numActuationsRun num Runs (5 ms gate)‏ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~0.02 Runs (3.2 ms gate)‏Beam Loss (V)‏

10 Preliminary analysis of data

11 Preliminary analysis of data

12 Preliminary analysis of data

13  Further analyses underway  Matching of beamloss and luminosity data likely to be made much more straightforward by new code written by Vassil Verguilov (to be tried out later today-!)‏  Luminosity Monitor is running at all times and therefore able to collect data in all runs Further Analyses

14  Simulations for the old target (10x1 mm 2 ) with different geometry using MARS and GEANT4 at 800 MeV yield: MARS simulation: GEANT4 simulation:  Good agreement with observed rate for MARS, GEANT4 simulations and unshielded detectors (LMC-12).  Even though these simulations were done using the old target, the average material in target is very similar: New target:  ( )=11.7 mm 2 Comparison to simulations Beam

15  We have run new simulations using G4Beamline  Set up cylindrical target (R=3mm,r=2.3mm), and two detectors 100x100cm 2, separated by 15 cm plastic at 10 m and 25 o angle. Include 6 mm thick steel from target enclosure New simulations Detectors Beam pipe Target

16  Only select particles within acceptance of detectors (100x100cm 2 at 10 m) and kill all other particles  Test that we don’t kill valid particles by changing kill volumes New simulations Proton Beam Target (yellow volumes)‏

17  Only select particles within acceptance of detectors (100x100cm 2 at 10 m) and kill all other particles  First run with QGSP hadronic model Comparison hadronic models Shielded detectors Unshielded detectors QGSP

18  Only select particles within acceptance of detectors (100x100cm 2 at 10 m) and kill all other particles  Now run with QGSP_BERT (QGSP+Bertini cascade model) for comparison Comparison hadronic models Shielded detectors Unshielded detectors QGSP_BERT

19  Compare number protons crossing unshielded detector (10 4 cm 2 ) for different hadronic models (up to a factor 2): Comparison hadronic models 2.50x QGSP_BIC 2.84x QGSP_BERT 1.56x QGSP 1.67x QGSC 3.20x LHEP_BERT 1.59x LHEP Protons/ (pot cm 2 )‏ In unshielded Area detector (cm 2 )‏ Protons on target (pot)‏ Number protons in unshielded detector Hadronic model

20  Compare number protons crossing unshielded detector (10 4 cm 2 ) for the two target geometries to understand normalisation  Compare new target (cylinder with outer radius 3 mm and inner radius 2.3 mm) with old target (10 mm x 1 mm)‏ Comparison target geometry  Volume material in each target is very similar (assume depth inside beam=10mm): Old target: 10x1x10 mm 3 New target:  ( )x10=116.7 mm 3 New Old

21  Compare number protons crossing unshielded detector (10 4 cm 2 ) for two target geometries (using QGSP_BIC)‏ Comparison target geometry 2.27x Old 2.74x New Protons/ (pot cm 2 )‏ Unshielded detector Area detector (cm 2 )‏ Protons on target (pot)‏ Number protons in unshielded detector Target geometry  There is a factor of ~8 difference in normalisation, but we need to take into account that old target has 10 mm thickness  New target has variable thickness due to geometry of cylinder (effective average thickness mm=116.7/60)‏  Need to correct for number protons that actually interact with target to correct for normalisation, but can estimate: (agreement not as good!)‏

22 Comparison of Target Geometry  The particle rates, normalised to protons on target differ by a factor 2.274/0.273=~8.32  Possible reasons:  Although the average material in each target is roughly equal, the volume traversed by the beam is not  Average thickness of new target: 1.16mm vs 10 mm for old - > less interactions  Ratio of particles interacting : /0.0051=~8.27  But this is not actually the number of p.o.t

23 Normalisation  With old target, protons lose 9 MeV/c on average, enough to lose the grip of the beam  With new target, 2 MeV/c. Will these particles be retained by the beam? ~2mrad average multiple scattering angle. Extensive further study required.

24  Luminosity Monitors have been installed in ISIS vault and are working properly  MOM now has instruction sheet to operate detectors  LM data scales very well with beam loss data  Calculation of protons on target from old simulation (for the old target) agrees with data from LM  Once further verification of scalar data and better understanding normalisation in simulations, we can use the LM scalar data to determine protons on target, independent of beamloss data Conclusion