luminosity monitor design mice collaboration meeting 31 may 2009 paul soler

Luminosity Monitor DesignLuminosity Monitor Design

MICE Collaboration Meeting 31 May 2009

Paul Soler

P Soler, MICE CM24, 31 May 2009

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Purpose of Luminosity MonitorsPurpose of Luminosity Monitors Alain gave good rationale for having luminosity monitors

during MICE run at Video Conference 9 April Use luminosity data to determine protons on target as

function of depth – independent of beam loss monitors Beam loss monitors have not been very stable as function

target depth – can be used to detect early problems target


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Purpose of Luminosity Monitors Purpose of Luminosity Monitors (cont.)(cont.)

Cross-correlate luminosity monitor (close to target), which measures mainly protons and pions, with other counters downstream (more sensitive to pions or muons)

Validation of beamline simulations

Comparison with beam-loss monitors to determine protons-on-target (pot)

BLM calibrations as function of KE:


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MARS Distributions at Scintillator MARS Distributions at Scintillator PlanePlane

Unshielded 5 cm polyethylene shielding

Simulations: 10 Million protons on MICE target, KE = 800 MeV (from 2006)

MARS yieldsin simulated area of 40x40 cm2 at 10 m distance

Number particles

Number particles

P (MeV/c) P (MeV/c)


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GEANT4 Distributions at Scintillator GEANT4 Distributions at Scintillator PlanePlane

Unshielded 5 cm polyethylene shielding

GEANT4 yieldsin simulated area of 40x40 cm2 at 10 m distance

Number particles

Number particles

Simulations: 10 Million protons on MICE target, KE = 800 MeV (from 2006)

P (MeV/c) P (MeV/c)


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Design consideration Luminosity Design consideration Luminosity MonitorsMonitors

Best way to monitor luminosity is by counting protons from target

15 cm plastic (5.5 cm Al) stops:— 500 MeV/c protons (R/M~16) — 150 MeV pions (R/M~110).

5 cm plastic (1.9 cm Al) stops:— 350 MeV/c protons (R/M~5.3)— 100 MeV/c pions (R/M~36)

To also stop neutrons, maybe add a thin layer of cadmium.


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Particle Counters in 2006Particle Counters in 2006Two sets of detectors at 10 m distance, 30o angle

- 1 pair of shielded scintillators: 3x3x30 mm3

(with 5 cm polyethylene shielding)- 1 unshielded pair of detectors: 10x10x10 mm3 - 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


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Data taking Nov 2006Data taking Nov 2006 Number of particles recorded by detectors during last 2 ms of spill

(KE=778+22-64 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 2.8x109 protons on target (calibration: 3.5x10-14 V s/proton at 9 ms with ~50% error)

Shielded detectorsUnshielded detectors


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For example, let’s take beam loss of 50 mV:

From MARS simulation at 780 MeV:

So, the expected number of singles in 1 cm2 is:

So, most particles observed in target test were protons Not surprising, since we had very little shielding If we want to discriminate integrated proton flux above

energy threshold then introduce shielding between first pair and second pair scintillators

Back of envelope calculationsBack of envelope calculations

potpotVs

sV 914

33

108.2/105.31021050

potpartcm

cmpot

protons /106.11600

110

261 82

2

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particlespotpotpart 45~108.2/106.1 98

(in last two milliseconds)

(compare to observed rate in slide 8)


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Particle Yields (Nov 2006)Particle Yields (Nov 2006) From MARS and GEANT4 simulation, calculate number of singles in

100 mm2 area of unshielded and 90 mm2 of shielded detectors from simulations of 107 pot in 1600 cm2, 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 1.70+-0.10(stat) 1.52+-0.10(stat) 0.894+-0.079

GEANT4 2.47+-0.12(stat) 1.61+-0.10(stat) 0.652+-0.051

DATA 1.59+-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


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Possible design of box for luminosity monitors:

Rate: for beam loss monitors running 50 times higher level (ie. beam loss ~2.5 V) would mean around 2000 particles/cm2 in final 2 ms of spill (ie ~1 MHz proton rate)

Proposed design of Luminosity Proposed design of Luminosity MonitorsMonitors

Cuts off protons ~300 MeV/c

Cuts off protons ~500 MeV/c

~2cm2

Thin layer Cd


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Use Hamamatsu H5783P PMTs: — Small, fast, high gain tubes— 0.8 ns rise time— ~1x106 gain— Packaged, so only need up to 15 V

PhotomultipliersPhotomultipliers

Cost: £632 per unit (we already have two units so should cost around £1300)

Readout: use NIM coincidence units and count using scalers (already implemented in DAQ, use spare channels)

Final issues: lay cables from MICE hall to ISIS vault and low voltage power supply

Aim to install on Q1 August 09 shutdown

50 mm


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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) It is a rather inexpensive addition to beamline If given approval can be delivered/installed in

August

ConclusionsConclusions

luminosity monitor design mice collaboration meeting 31 may 2009 paul soler

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