Beam Test of Moller Main Detector Prototype

Peiqing WangMichael Gericke

University of Manitoba

Moller Collaboration MeetingOct. 22, 2013

2

Prototype Detector Geometry

Schematics (not in scale)

PMT

5 cm

4 cm

8.4

cm

30 cm 25, 35 or 60 cm

PMT/base Housing Light Guide

Quartz

4 cm

2.54

cm

3

Quartz Radiators

Size: 8 cm x 6 cm x 2.5 cm

Identification:

Q1: with a single 45 deg cut

Q2: with two 45 deg cuts

Q3: no angle cut

2.5 cm6

cm

8 cmQ1 Q2 Q3

The cutted side is facing light guide Hand-polished (not in high quality)3 different shapes to test which one has the best light yield

4

Light Guide & PMT Housing

8 light guides were built with different materials and lengthes

● UVS: 25 cm, 35 cm, 60 cm● Miro-2: 25 cm, 35 cm● Miro-Silver: 25 cm, 35 cm, 60 cm

A wider light guide opening (4 cm) allows to fit thicker quartz (2.54 cm) with different tilt angles

A larger PMT housing (30 cm x 9 cm x 9 cm) allows to hold 3” or 2” PMT and base

Considering the flexibility of changing configurations for prototype tests ...

60 cm 35 cm

25 cm

5

Light Guide and Quartz Housing

Looking inside from the opening of PMT housing(the bright shining part is the light guide section)

Quartz housing:

● Small container to hold our short quartz piece

● Easier to change light guide with a spearated quartz housing

● Top trapezoid section allows quartz to tilt from 0 to 45 deg

● Bottom section fits the shape of light guide

“top endcap + black tape + bottom endcap” to make it light tight

Considering the flexibility of changing configurations for prototype tests ...

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Quartz and Detector Mounting

Quartz mounting:● Alllowing to mount quartz at different

orientation angles (0 – 45 deg)● Easily to exchange quartz

Detector mounting:● Allowing to mounting detector at different

orientation angles and positions(30, 45, 60, 90, 120, 135 and 150 deg)

● With ability to adjust height

Quartz mounting bracket

Detector mounting structure

7

Photomultiplier Tube9305KFL (SN509) by ElectronTubes

3 inch (78 mm), active diameter 70 mm

Operating HV: 1700 V (maximum)

High QE at UV band

Quantum Efficiency of 9305KFL (SN509)

8

Beam Test Setup at MAMI Facility

Side View Looking Downstream

● Detector tilted 45 deg from beam pipe● Beam going throung quartz

● Detector tilted 135 deg from beam pipe● Beam going throung light guide

● Mounted on a 2D motion table (range: horizontal 0 – 14 cm, vertical 0 – 10 cm)● Light guide tilt angle was defined as the angle between beam pipe and light guide

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Electronics/DAQ

Detector

Scintillator 1

Scintillator 2

Disc

Disc

Amplifier

And

Delay

Delay

QDC

gate

ch0

ch1

● Ch1 is an amplified copy of Ch0

● QDC: CAEN V965, ~900 pC full range

● Trigger rate: 3 – 5 kHz, typical run time: 300 s

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Tests and Studies Performed

● Calibrations (QDC sensitivity, amplifier gain and SPE)● Light yield with the most “realistic” configuration● Hit-position-dependent light yield● Detector excess noise● Effects of quartz polishing quality● Light guide length and material● Quartz & LG geometry● Quartz wrapping material● Lead pre-radiator, effects of shower in quartz and in LG● Background events in light guide● Blacked-out LG studies● PMT type selection

11

Calibration: QDC Sensitivity, Amplifier Gain and SPE

QDC (CAEN V965) sensitivity: 0.2 pC/chcalibrated by using 120pC charge pulser

Amplifier Gain: 13.7determined by comparison of non-amplified signals in channel 0 and amplified signals in channel 1

SPE charge: 0.35 +/- 0.07 pC (at normal operating HV - 1250 V)

Method 1 (cross-calibration technique): 0.3 pC/PE Directly observed SPE (~2.7 pC/PE at 1.7 kV) by pushing PMT to its highest gain, then cross-calibrated it back to its normal operating HV (1250 V) via two fixed configuration runs at both high and low HVs. Uncertainty depends on fit quality.

Method 2 (LED calibration technique): 0.4 pC/PE, Uncertainty depends on fit quality.

Method 3 (statistical method): 0.42 pC/PE, This is the upper bound of SPE charge, calculated from measured detector resolution.

Taking average of 1 & 2, then imposing a systematic error bar on the average so that it can reach the upper bound, i.e. SPE = 0.35 +/- 0.07 pC

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The Most “Realistic” Configuration

Configuration:

PMT: SN509HV: 1250 VSPE: 0.35 pC/PE in ch0 at 1250 Vquartz: 1 cm thick, wrapped with white paper, single 45 deg cut at light guide sideLG: Miro Silver 25 cm, 45 deg tilt vs beamQDC: CAEN V965, sensitivity 0.2 pC/ch

PMT

beam

Test the Umass' 1 cm thick, well-polished quartz in Manitoba light guide

● This configuration was mostly close to the intended design of Moller ring detector

● Configuration differences between simulation and beam test:

Simulation Beam Test

Light guide UVS, 35 cm long Miro-Silver, 25 cm long

Quartz 1.5 cm thick 1 cm thick

PMT Low QE Higher QE in UV band

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Run#410

Ped: 61.9

Gaussian fit:Peak: 117.4Sigma: 11.2

● Simulation expectation: 37 PE ( for 1.5 cm thick quartz) 25 PE ( for 1.0 cm thick quartz)

(ref. p.21, Moller DocDB#76-v1)

● Data: (117 - 62) x 0.2 pC/ch / (0.35+/-0.07) pC/PE = 31 PE (or 26 - 39 PE)

● Good agreement. A little bit higher #PE yield in test data can be attributed to shorter light guide, better reflectivity, and higher PMT QE

Full spectrum with pedestal removed:Mean: 121.1RMS: 16.7

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Hit-Position-Dependent Light Yield – Horizontal Scan

● Beam position scan from left to right on quartz (beam's eye view)

● Yield increases a little when beam moving to the light guide side; this could attribute to the polishing quality of quartz.

● As expected, yield decreases at the slope on quartz, and is propotional to the the thickness of quartz

Light guide side

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Hit-Position-Dependent Light Yield – Vertical Scan

● Beam position scan from bottom to top on quartz (beam's eye view, here from left to right)

● #PE yield reaches maximum at quartz center

● The yield differences is ~7%; this could also attribute to the polishing quality of quartz.

beam

quartz

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Excess Noise

● Beam energy: 0.9 GeV

● Data point at 1 cm thickness of quartz was obtained from UMass' well-polished quartz

● Mean and RMS were obtained from pedestal-removed QDC spectrum

Simulation Expectation: ~5%

Beam Test Data: <6%

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Quartz Geometry

beam

beam

● Both configurations used a same Miro-Silver 25 cm long light guide

● Single-cut quartz (Q1) has better performance

● #PE Yield ratio: 81.7%

Q1

Q2

PM

T

PMT

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Quartz Wrapping Material

No wrapping

Mylar

Whitepaper

● #PE yield ratio: 1 : 1.9 : 3.2 (No wrapping : Mylar : White paper)

● Large effect on #PE yield (due to quartz polishing quality?)

PMT

beam

Quartz: Manitoba Q1 (2.5 cm)LG: Miro-Silver 25 cmPMT: 3” (ET #509)

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Quartz Polishing Quality

PMT

beam1 cm thick quartzwell polished

2.5 cm thick quartzhand-polished

● #PE Yield ratio (2.54 cm quartz: 1 cm quartz):

2.17 : 1

● Loss due to polishing quality:

(2.54 - 2.17)/2.54 = ~15%

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Lead Pre-radiator

PMT

beam

● Lead pre-radiator (1.5 cm thick) increases the #PE yield by a factor of 5.6

● Excess noise:~5% (no lead)~10% (with lead)

1.5 cm thick lead

no lead

with lead

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Light Guide Length

60 cm long Miro-Silver(run#109)

25 cm long Miro-Silver(run#58)

Compare the yields of 60 cm and 25 cm light guides:

#PE Yield Ratio: 68%

PMT

beam

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Light Guide Material

25 cm long UVS(run#184)

25 cm long Miro-Silver(run#182)

Compare the yields of UVS and Miro-Silver 25 cm light guides:

#PE Yield Ratio: 92.6%

beam

Miro-Silver is 7% better than UVS

PM

T

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Light Guide Events

● Red: "1 cm quartz + 1.5 cm lead" in front of light guide. Because this "shower-booster" was 45 deg tilted w.r.t. beam, it is equivlent to:

1.4 x (1 cm quartz + 1.5 cm lead)

● Green: 1.0 cm thick quartz in front of light guide, ~1.4 cm equivlent thickness due to 45 deg tilting angle

● Blue: no pre-rad material in front of light guide.

● bkg events can be clearly seen,

● the upstream shower from quartz and lead increased these bkg events dramatically (quantitative studies needed).

full range is about 200 PEs

PMT

beam

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Blacked-out Light Guide

beam

PM

T

25 cm long light guide lining with black Kapton

Using “black” light guide to test: contributions from the “line-of-sight” photons

#PE yield ratio:

~9% (kapton : Miro-Silver)

black Kapton light guide

Miro-Silver light guide

More than 90% detected photons propogate via the reflection of light guide

(note: black kapton is not an ideal material for blacked-out)

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Blacked-out Light Guide

Red: Miro-Silver 45 deg

Green: Kapton, 45 deg

Blue: beam-off pedestal

Comparison of light guide events in Miro-Silver light guide and blacked-out light guide

beam

PM

T

25 cm long light guide lining with black Kapton

● Tails above pedestal can be seen

● Black Kapton light guide has a smaller tail

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Blacked-out Light Guide

beam

PM

T

Light guide Lining: black Kapton

Cyan: 90 deg

Red: 45 deg

Blue: 90 deg with 1 cm thick quartz in front

Green: 135 deg

PMT

PMT

45 deg 90 deg 135 deg

Comparison of blacked-out light guide events at different light guide orientation angles

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PMT Type

Blue (3” PMT):

● ET 9305KFL● Active diameter: 70 mm● High QE (~30%) at UV● Shorter light guide: 25 cm

Red (2” PMT)

● Photonis XP2268● Active diameter: 44 mm● Lower QE at UV● Longer light guide: 35 cm

2” PMT

3” PMT

For comparison:

● Normalized● Converted to #PE

#PE yield:

● 2” - 17.3 PE● 3” - 65 PE (or >55 PE)

#PE yield ratio 3.75 : 1

(PMT acceptance: 2.53 : 1 )

From simulation, an effective way to increase the #PE yield is to increase PMT acceptance

Test configuration: Q1 quartz (1inch), Miro-Silver light guide with 45 deg orientation angle

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Conclusion

● A fruitful test beam experiment - many studies were performed

● Not all tests are covered here; data for a few more configurations are available for analysis

● Preliminary analysis showed a general agreement between beam test data and detector simulation expectations

● For a configuration with 1 cm thick, well-polished quartz, we obtained

#PE > 25, excess noise ~4%

● Light guide events were confirmed; further quantitative studies are needed

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Calibration of QDC Sensitivity and Amplifier Gain

QDC: CAEN V965, 900 pC full range

Charge of pulse: 120 pC

Pedestal is in channel 136.1

Peak of charge pulses is in channel 737.9

QDC sensitivity: 120 pC/(737.9 - 136.1) = 0.2 pC/ch

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no amplifier

with amplifier

Determination of Amplifier Gain

● Ch0: no amplifier

Ch1: amplified copy of ch0

● Fit pedestal and peak

Ch1 mean – ped.● Gain = ------------------------- = 13.7 Ch0 mean – ped.

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Configuration:

PMT: SN509HV: 1250 VSPE: 0.35 pC/PE in ch0 at 1250 VQuartz: 2.5 cm thick, wrapped with white paper, single 45 deg cut at light guide sideLG: Miro Silver 25 cm, 45 deg tilt vs beamQDC: CAEN V965, sensitivity 0.2 pC/ch

PMT

beam

Using the 1 inch thick quartz

#PE Yield of the “Best” Configuration

#PE Yield: 65 PE

(or 55 – 82 PE if taking into account the uncertainty of SPE calibration)