Luminosity MonitorLuminosity MonitorLuminosity MonitorLuminosity Monitor

UKNF Meeting 7 June 2010

Paul Soler, David ForrestDanielle MacLennan

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Purpose of Luminosity MonitorsPurpose 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

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Final design of luminosity monitor:

Luminosity Monitor DesignLuminosity Monitor Design

Beam

Cuts off: protons ~500 MeV/c pions ~150 MeV/c

(6 mm thick)

(6 mm thick)

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Final design of luminosity monitor:

Luminosity Monitor DesignLuminosity Monitor Design

Beam

Cuts off: protons ~500 MeV/c pions ~150 MeV/c

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PMTs: Hamamatsu H5783P— 0.8 ns rise time— ~1x106 gain— Only need to provide <15V to power PMT

Readout: use NIM coincidence units and count three channels using VME scalers already in DAQ

PhotomultipliersPhotomultipliers

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

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Installation of Luminosity MonitorsInstallation of Luminosity Monitors Installation of Luminosity Monitor: 12-15 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

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Installation of Luminosity MonitorsInstallation of Luminosity Monitors

Position of luminosity monitor:10 m from target at 25o.

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Commissioning Luminosity MonitorsCommissioning Luminosity Monitors Commissioning was performed in 12-15 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)

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Commissioning Luminosity MonitorsCommissioning Luminosity Monitors Runs performed 7 February (many thanks to Terry,

Pierrick, Adam and Vassil for help during shift!)

ActuationsRun numActuationsRun num

1458

1459

1461

1462-1464

1457

1447

1448

1449

1450

1451

1452

1453

1454

1455

1456

Runs (5 ms gate)

345100~1.5

410100~2.0

572101~1.0

769100~0.75

100~0.50

101~0.40

200~0.30

201~0.20

200~0.10

200~0.05

500 ~0.02

Runs (3.2 ms gate)Beam Loss (V)

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Preliminary analysis of dataPreliminary analysis of data

Luminosity Monitor Commissioning RunsCoincidence of PMTs 1,2

y = 1955x - 268.3

0

1000

2000

3000

4000

5000

6000

0 0.5 1 1.5 2 2.5 3

Beamloss S7 Integral method (Vms)

Sca

lar

for

Co

inci

den

ce o

f P

MT

1, 2

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Preliminary analysis of dataPreliminary analysis of data

Luminosity Monitor Commissioning RunsCoincidence of PMTs 3, 4

y = 2086.4x - 402.35

0

1000

2000

3000

4000

5000

6000

0 0.5 1 1.5 2 2.5 3

Beamloss Sec7 Integral Method

Sc

ala

r o

f C

oin

cid

en

ce

of

PM

Ts

3 a

nd

4

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Luminosity Monitor Commissioning RunsCoincidence of PMT 1,2,3,4

y = 888.59x - 281.25

0

500

1000

1500

2000

2500

0 0.5 1 1.5 2 2.5 3

Beamloss Sec7 Integral Method

Sc

ala

r o

f C

oin

cid

en

ce

of

PM

T 1

2 3

4

Preliminary analysis of dataPreliminary analysis of data

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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 AnalysesFurther Analyses

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Simulations for the old target (10x1 mm2) 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: (3.02-2.32)=11.7 mm2

Comparison to simulationsComparison to simulations

potpartcm

cm

pot

protons/1063.1

1600

1

10

261 82

2

7

potpartcm

cm

pot

protons/1089.1

1600

1

10

303 82

2

7

Beam

Beam

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We have run new simulations using G4Beamline Set up cylindrical target (R=3mm,r=2.3mm), and two

detectors 100x100cm2, separated by 15 cm plastic at 10 m and 25o angle. Include 6 mm thick steel from target enclosure

New simulationsNew simulations

Detectors

Beampipe

Target

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Only select particles within acceptance of detectors (100x100cm2 at 10 m) and kill all other particles

Test that we don’t kill valid particles by changing kill volumes

New simulationsNew simulations

Proton Beam

Target

(yellow volumes)

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Only select particles within acceptance of detectors (100x100cm2 at 10 m) and kill all other particles

First run with QGSP hadronic model

Comparison hadronic modelsComparison hadronic models

Shielded detectorsUnshielded detectors

QGSPQGSP

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Only select particles within acceptance of detectors (100x100cm2 at 10 m) and kill all other particles

Now run with QGSP_BERT (QGSP+Bertini cascade model) for comparison

Comparison hadronic modelsComparison hadronic models

Shielded detectorsUnshielded detectors

QGSP_BERTQGSP_BERT

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Compare number protons crossing unshielded detector (104 cm2) for different hadronic models (up to a factor 2):

Comparison hadronic modelsComparison hadronic models

2.50x10-910410925014QGSP_BIC

2.84x10-910410928550QGSP_BERT

1.56x10-910410915577QGSP

1.67x10-9104107167QGSC

3.20x10-9104107320LHEP_BERT

1.59x10-9104107159LHEP

Protons/ (pot cm2)

In unshielded

Area detector (cm2)

Protons on target (pot)

Number protons in unshielded detector

Hadronic model

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Compare number protons crossing unshielded detector (104 cm2) 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 geometryComparison target geometry

Volume material in each target is very similar (assume depth inside beam=10mm):

• Old target: 10x1x10 mm3

• New target: (3.02-2.32)x10=116.7 mm3

New Old

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Compare number protons crossing unshielded detector (104 cm2) for two target geometries (using QGSP_BIC)

Comparison target geometryComparison target geometry

2.27x10-816001083323Old

2.74x10-910410925014New

Protons/ (pot cm2)

Unshielded detector

Area detector (cm2)

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 1.945 mm=116.7/60)

Need to correct for number protons that actually interact with target to correct for normalisation, but can estimate:

)/(103.1~1050.2945.1

10~ 289 cmpotprotons

(agreement not as good!)

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Comparison of Target GeometryComparison 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 : 0.0422/0.0051=~8.27

But this is not actually the number of p.o.t

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NormalisationNormalisation 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.

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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

ConclusionConclusion