1. Luminosity Monitors MICE Video Conference 7 May 2009 Paul Soler

2. 2 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 Reminder: Target test Nov 2006  Data taking: ̶ Tested prototype target with pulsed (varying delay on start of pulse) and stationary target ̶ Measured beam loss at the beam edge as target intersects beam for each time slice ̶ Cross-correlated with particle counters Depth from centre of beam (mm) Time x10 -4 s from ISIS Injection RED >0.4 extraction Stationary target Colour scale: Beam loss (arbitrary units) Pulsed target Combined plot of beam loss for all time slices Beam profile at edge

3. 3 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 Particle Counters in 2006  Two sets of detectors at 10 m distance, 30 o angle ̶ 1 pair of shielded scintillators: 3x3x30 mm 3 (with 5 cm polyethylene shielding) ̶ 1 unshielded pair of detectors: 10x10x10 mm 3 ̶ Scope DAQ and readout to Linux PC via GPIB  Signals from scintillators and ISIS read out recorded using oscilloscopes for each 10 ms burst Unshielded detectors Position of detectors (same angle as MICE beam)  Discrimination and coincidence of each scintillator pair performed offline Example of coincidence

4. 4 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 MARS Distributions at Scintillator Plane MARS Distributions at Scintillator Plane Unshielded 5 cm polyethylene shielding  Simulations: 10 Million protons on MICE target, KE = 800 MeV MARS yields in simulated area of 40x40 cm 2 Number particles P (MeV/c)

5. 5 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 GEANT4 Distributions at Scintillator Plane Unshielded 5 cm polyethylene shielding GEANT4 yields in simulated area of 40x40 cm 2 Number particles  Simulations: 10 Million protons on MICE target, KE = 800 MeV P (MeV/c)

6. 6 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009  Efficiency of detecting particles: simulate coincidence in both scintillators.  Majority of charged particles are protons.  Neutron efficiency given by: With: Detection Efficiency Detection Efficiency MARS efficiencies GEANT4 efficiencies ( 3% accuracy 0<E n <30 MeV) Neutron efficiency

7. 7 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 Data taking Nov 2006  Data recorded for stationary (fixed position) target and pulsed target (varying delay on start of pulse)  Fixed target produces particles in detectors at beginning of spill  Pulsed target produces particles in detectors as it follows beam envelope during beam acceleration 0  10 ms. Shielded detectors Fixed target Unshielded detectors Pulsed target Fixed target Pulsed target 8-10 ms Note that we had limited statistics!

8. 8 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 Data taking Nov 2006  Number of particles recorded by detectors during last 2 ms of spill (KE=778 +22 -64 MeV) important for MICE running  Correlation between beam loss and number of particles in last 2 ms of spill recorded by detectors  50 mV integrated beam loss signal corresponds to 2.8x10 9 protons on target (calibration: 3.5x10 -14 V s/proton at 9 ms with ~50% error) Shielded detectors Unshielded detectors

9. 9 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 Particle Yields (Nov 2006)  From MARS and GEANT4 simulation, calculate number of singles in 100 mm 2 area of unshielded and 90 mm 2 of shielded detectors from simulations of 10 7 pot in 1600 cm 2, with simulated efficiencies  From data, use slope of particles/beam loss plot and convert into particles/pot, using calibration.  We found good agreement between data, MARS and GEANT4, compatible within systematic errors of calibration (~50%). Singles/pot (Unshielded) (x10 -8 ) Singles/pot (Shielded) (x10 -8 ) Ratio * Shielded/ Unshielded MARS1.70+-0.10(stat)1.52+-0.10(stat)0.894+-0.079 GEANT42.47+-0.12(stat)1.61+-0.10(stat)0.652+-0.051 DATA1.59+-0.24(stat)+- 0.81(syst) 1.29+-0.22(stat)+- 0.65(syst) 0.81+-0.18 * Systematic error due to the calibration of the beam loss monitors cancels in the ratio All described in MICE-NOTE-227

10. 10 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 Luminosity Monitors for MICE run o Alain gave a good rationale for having luminosity monitors during MICE run at last VC o Useful to have luminosity data to determine protons on target as a function of depth – can determine this independent of beam loss monitors o Beam loss monitors have not been very stable as function target depth

11. 11 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 Luminosity Monitors for MICE run o Cross-correlate luminosity monitor (close to target) which measures mainly protons and pions with other counters downstream (more sensitive to pions or muons) o Validation of beamline simulations o Comparison with beam-loss monitors to determine protons- on-target (pot) BLM calibrations as function of KE:

12. 12 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 o For example, let’s take beam loss of 50 mV: o From MARS simulation at 780 MeV: o So, the expected number of singles in 1 cm 2 is: o So, most particles observed in target test were protons o To count pions, need to shield from protons: that was why we had shielded and unshielded before, but need more plastic Back of envelope calculations (in last two milliseconds) (compare to observed rate in slide 8)

13. 13 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 o Alain showed last VC that 15 cm of plastic stops: — 500 MeV/c protons — 150 MeV pions. o However, protons extend up to 1200 MeV/c so need more plastic, or denser material to stop all protons (tungsten loaded plastic looks expensive and not easily available) o For example R/M~100 implies — ~30cm Al, 13 cm steel — Stopping pions ~200 MeV/c o To also stop neutrons, maybe add a thin layer of cadmium. Design of Luminosity Monitors (in last two milliseconds)

14. 14 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 o Alain showed possible design of luminosity monitors: o For beam loss monitors running 50 times higher rate (ie. beam loss ~2.5 V) would mean around 2000 particles/cm 2 in final 2 ms of spill (ie 1 MHz proton rate) o However, pions are between 3%-10% of protons, so would be around 100 kHz (for 4 cm 2 of scintillator then pion rate less than 400 kHz). o Exact level of shielding will determine ratio of pions to protons measured: this should be a design consideration Design of Luminosity Monitors

15. 15 Luminosity Monitors P Soler, MICE Video Conference, 7 May 2009 o Use Hamamatsu H5783P PMTs: — Small, fast, high gain tubes — 0.8 ns rise time — ~1x10 6 gain — Packaged, so only need up to 15 V Photomultipliers o Cost: £632 per unit (we already have two units so should cost around £1300) o Readout: add 4 TDC channels to DAQ or count rate using scalers (easier) 50 mm