PREX main detector
PREx Collaboration Meeting
Feb. 19-20, 2010
Aimee Shore
Kumar Krishna
Jon Wexler
Patrick Rogan
Vireak Yim
Smith College
UMass
Piotr Decowski
Outline
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Detector assembly in HRS focal plane
Detector head and its optimization
AT - hole detector
Progress of construction
Other tasks
Issues
Detector assembly
Quartz blocks
and reflectors
Detector assembly, cont.
All dimensions and positioning in respect to the VDC
are 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
GEMs
Trigger
Main detectors
X-Y movers
Unistrut support
Another view
GEM support details
GEMs
Supports for electronics
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 jet
cutter, which wil be used to cut more elaborated shapes.
Location of the main detector head in the HRS focal plane
(Dustin’s simulations)
Detector head
14 cm long
and 3.5 cm
wide quartz
PMT
Quartz holder bar at save
distance from the beam
(no beam splash)
Detector head: Optimization of reflector
Geometry
14 cm long quartz
GEANT simulations:
- range of reflectivity
coefficients
- specular versus diffuse
reflection
PMT
Tube
Conical mirror
Results of Simulations
Specular reflection
Diffuse reflection
htemp
Pepm1:Beamx-36.5 {Pepm1>0}
Entries
Mean
Meany
120
2620
6.675
98.89
3.868
18.36
Refl: 100% RMS
RMSy
100
80
PMT
side
100
Painted cone
80
Al cone
X dependence
of PE number
(dispersive
direction)
Refl: 90%
60
Refl: 80%
Refl: 70%
40
htemp
Pepm1:Beamx-36.5 {Pepm1>0}
14 cm * 4 cm quartz
Entries
Mean
Meany
3070
6.819
75.04
3.894
15.68
RMS
RMSy
Refl: 100%
60
Refl: 90%
PMT
side 40
Refl: 80%
Refl: 70%
No mirrors
No mirrors
20
20
0
0
2
4
Pepm1:Beamy {Pepm1>0}
100
These regions were tested
using cosmic rays
Entries
4
6
8
10
12
14
X distance along quartz (cm)
Mean
0.004606
Meany
98.89
RMS
1.163
RMSy
18.36
Al cone
3070
0.004666
Meany
80
RMS
RMSy
70
Y dependence
of PE number
(transverse
direction)
40
60
50
40
30
For typical reflectivity 80 - 90 % Painted
expected number of PEs ~ 50 - 60
20
20
htemp
Entries
2620
60
0
2
Pepm1:Beamy {Pepm1>0}
htemp
Mean
80
0
0
6
8
10
12
14
X distance along quartz (cm)
cone
10
-2
-1.5
-1
-0.5 0 0.5 1 1.5 2
Y distance across quartz (cm)
0
-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2
Y distance across quartz (cm)
75.04
1.17
15.68
Setup for cosmic tests
Quartz made from 6 smaller pieces
PMT
Lead filter
One of the trigger detectors
Results from cosmic tests
Region 2
sqrt(PE)
Al cone
No mirrors
Flat Al mirrors
Painted cone
White paper cone
Wrapped mylar
Painted quartz
Painted flat mirrors
Region 1
Region 2
Region 1
Number of PEs
Painted flat mirrors
Painted cone
White paper cone
Flat Al mirrors
Painted quartz
Al cone
Wrapped mylar
No mirrors
Best: Painted flat mirror?
Painted quartz?
Paint
100
40
250 nm
2500 nm
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
Issues
The most serious problem is uncertainty in delivery
time of ordered quartz blocks. They should be
delivered before the end of February, however,
the manufacturer informed us that there will be a delay
caused by bandsaw failure. The projected delivery time
is 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.