Luminosity Monitor Design MICE Collaboration Meeting 31 May 2009 Paul Soler

2 P Soler, MICE CM24, 31 May 2009 Purpose of Luminosity Monitors o Alain gave good rationale for having luminosity monitors during MICE run at Video Conference 9 April o Use luminosity data to determine protons on target as function of depth – independent of beam loss monitors o Beam loss monitors have not been very stable as function target depth – can be used to detect early problems target

3 P Soler, MICE CM24, 31 May 2009 Purpose of Luminosity Monitors (cont.) 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:

4 P Soler, MICE CM24, 31 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 (from 2006) MARS yields in simulated area of 40x40 cm 2 at 10 m distance Number particles P (MeV/c)

5 P Soler, MICE CM24, 31 May 2009 GEANT4 Distributions at Scintillator Plane Unshielded 5 cm polyethylene shielding GEANT4 yields in simulated area of 40x40 cm 2 at 10 m distance Number particles  Simulations: 10 Million protons on MICE target, KE = 800 MeV (from 2006) P (MeV/c)

6 P Soler, MICE CM24, 31 May 2009 Design consideration Luminosity Monitors o Best way to monitor luminosity is by counting protons from target o 15 cm plastic (5.5 cm Al) stops: — 500 MeV/c protons (R/M~16) — 150 MeV pions (R/M~110). o 5 cm plastic (1.9 cm Al) stops: — 350 MeV/c protons (R/M~5.3) — 100 MeV/c pions (R/M~36) o To also stop neutrons, maybe add a thin layer of cadmium.

7 P Soler, MICE CM24, 31 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

8 P Soler, MICE CM24, 31 May 2009 Data taking Nov 2006  Number of particles recorded by detectors during last 2 ms of spill (KE= MeV) when target expects to dip in beam  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: 3.5x V s/proton at 9 ms with ~50% error) Shielded detectors Unshielded detectors

9 P Soler, MICE CM24, 31 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 Not surprising, since we had very little shielding o If we want to discriminate integrated proton flux above energy threshold then introduce shielding between first pair and second pair scintillators Back of envelope calculations (in last two milliseconds) (compare to observed rate in slide 8)

10 P Soler, MICE CM24, 31 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 MARS (stat) (stat) GEANT (stat) (stat) DATA (stat) (syst) (stat) (syst) * Systematic error due to the calibration of the beam loss monitors cancels in the ratio All described in MICE-NOTE-227

11 P Soler, MICE CM24, 31 May 2009 o Possible design of box for luminosity monitors: o Rate: for beam loss monitors running 50 times higher level (ie. beam loss ~2.5 V) would mean around 2000 particles/cm 2 in final 2 ms of spill (ie ~1 MHz proton rate) Proposed design of Luminosity Monitors Cuts off protons ~300 MeV/c Cuts off protons ~500 MeV/c ~2cm 2 Thin layer Cd

12 P Soler, MICE CM24, 31 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: use NIM coincidence units and count using scalers (already implemented in DAQ, use spare channels) o Final issues: lay cables from MICE hall to ISIS vault and low voltage power supply o Aim to install on Q1 August 09 shutdown 50 mm

13 P Soler, MICE CM24, 31 May 2009 o Luminosity monitors will really help in the commissioning of the beamline — Will allow us to understand the protons on target as function of target depth with high accuracy — System designed to monitor secondary protons from target (>300 MeV/c and >500 MeV/c) o It is a rather inexpensive addition to beamline o If given approval can be delivered/installed in August Conclusions