PREX main detectorPREX main detector

Piotr Decowski

Aimee Shore

Smith College

Piotr Decowski

Aimee Shore

Smith College

Kumar Krishna Jon Wexler

Patrick RoganVireak Yim

UMass

Kumar Krishna Jon Wexler

Patrick RoganVireak Yim

UMass

PREx Collaboration MeetingFeb. 19-20, 2010PREx Collaboration MeetingFeb. 19-20, 2010

Outline

• Detector assembly in HRS focal plane• Detector head and its optimization

• AT - hole detector

• Progress of construction• Other tasks• Issues

Detector assembly

Beam

Two pa

irs o

f GEM

s

Two m

ain

dete

ctors

Scintillator trigger

Quartz blocksand reflectors

Detector assembly, cont.

All dimensions and positioning in respect to the VDCare determined and fixed. The information about exact detector position will allow to finalize details of beam optics in the HRS hut (John LeRose)

Detector assembly mounted in the HRS focal plane

Trigger

Main detectors

Beam

X-Y movers

Unistrut support

GEMs

Another view

GEM support details

GEMs

ElectronicsSupports for electronics

These parts will be machined in the Umass, UVA, and Smith College shops.Smith College’s shop is equipped with computer controlled powerful water jetcutter, which wil be used to cut more elaborated shapes.

Location of the main detector head in the HRS focal plane(Dustin’s simulations)

Quartz holder bar at save distance from the beam

(no beam splash)

Detector head

PMT

14 cm longand 3.5 cm wide quartz

Detector head: Optimization of reflector

14 cm long quartz

Conical mirror

PMT

Tube

GEANT simulations:- range of reflectivity coefficients- specular versus diffuse reflection

Geometry

htempEntries 2620

Mean 0.004606

Meany 98.89

RMS 1.163

RMSy 18.36

Y distance across quartz (cm)-2 -1.5 -1 -0.5 0 0.5 1 1.5 20

20

40

60

80

100

htempEntries 2620

Mean 0.004606

Meany 98.89

RMS 1.163

RMSy 18.36

Pepm1:Beamy {Pepm1>0}

Al cone

htempEntries 3070

Mean 0.004666

Meany 75.04

RMS 1.17

RMSy 15.68

Y distance across quartz (cm)-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 20

10

20

30

40

50

60

70

80

htempEntries 3070

Mean 0.004666

Meany 75.04

RMS 1.17

RMSy 15.68

Pepm1:Beamy {Pepm1>0}

Painted cone

htempEntries 2620

Mean 6.675Meany 98.89

RMS 3.868RMSy 18.36

X distance along quartz (cm)0 2 4 6 8 10 12 140

20

40

60

80

100

120

htempEntries 2620

Mean 6.675Meany 98.89

RMS 3.868RMSy 18.36

Pepm1:Beamx-36.5 {Pepm1>0}

Refl: 100%

Refl: 90%

Refl: 80%

Refl: 70%

No mirrors

Al cone

htempEntries 3070

Mean 6.819Meany 75.04

RMS 3.894RMSy 15.68

X distance along quartz (cm)0 2 4 6 8 10 12 140

20

40

60

80

100

htempEntries 3070

Mean 6.819Meany 75.04

RMS 3.894RMSy 15.68

Pepm1:Beamx-36.5 {Pepm1>0}

Refl: 100%

Refl: 90%

Refl: 80%Refl: 70%

No mirrors

Painted cone

Results of Simulations

X dependenceof PE number(dispersive direction)

Y dependenceof PE number(transversedirection)

Specular reflection Diffuse reflection

These regions were testedusing cosmic rays

PMTside

PMTside

14 cm * 4 cm quartz

For typical reflectivity 80 - 90 %expected number of PEs ~ 50 - 60

Setup for cosmic testsQuartz made from 6 smaller pieces

PMT Lead filter

One of the trigger detectors

Results from cosmic testsR

egio

n 1

Reg

ion

1

Reg

ion

2

Num

ber

of

PE

s

sq

rt(P

E)

Painted flat mirrorsPainted coneWhite paper coneFlat Al mirrorsPainted quartzAl coneWrapped mylarNo mirrors

Al coneNo mirrorsFlat Al mirrorsPainted coneWhite paper coneWrapped mylarPainted quartzPainted flat mirrors

Best results

Reg

ion

2

Best: Painted flat mirror? Painted quartz?

Paint

250 nm 2500 nm40

100

AT - hole detector

Separate detector on X - Y movers attached to the 45 deg side yellow beam of the focal plane cage.

4 cm * 4 cm quartz tangent to the Cherenkov cone. Detector axis in the beam - y axis plane, at angle 45 deg in respect to the beam.

Dustin’s plots

Status of the detector construction

- Most of the parts for detector heads are ready

- The design of the detector assembly is finalized,

drawings are in the final stage and in the next few

days will be given to the machine shop

- PMTs are purchased

- PMT bases must be modified to be able to

accommodate -2000V, out of 9 bases 4 are ready

- Quartz and movers are ordered

Other tasks

- Setup for measurements of gains of all PMTs by single photon counting is ready, we are still waiting for return of CAEN ADC from repair in Italy

- Blue LEDs are purchased and will be mounted in the detector heads for in beam monitoring of PMT linearity

IssuesThe most serious problem is uncertainty in deliverytime of ordered quartz blocks. They should be delivered before the end of February, however, the manufacturer informed us that there will be a delaycaused by bandsaw failure. The projected delivery timeis now the beginning of the second week of March.

For any case we are preparing four 13.4 cm long pieces of quartz, each made from 6 smaller pieces.