Focal Plane Scanner

Focal Plane ScannerJeff Martin

University of Winnipegwith: Jie Pan, Peiqing Wang, David Harrison

Motivation

• Q2 determination, background studies, all done at 10 nA using tracking system.

• Region III operable up to 100 nA.

• Qweak production running 180 A.

• Need a way to extrapolate over 3 orders of magnitude.

Qweak Focal Plane Scanner• A scanning detector with small active area

to sense high-energy electrons, operable at any beam current.

• Similar technique used in E158 and HAPPEx.

• For E158, it was used to determine optics parameters, confirm Monte Carlo predictions of rates.

Scanner Principle

Design criteria:• 1 cm2 active area.• 1 MHz max rate allows operation in

counting mode with two PMT’s.• operable at both high and low current.scattered

electrons

Č

PMT

air-corelight pipe

quartzradiator

pre-rad

Scanner Concept

scatteredelectrons

side view beam view

Implementation in Qweak

• 2D motion assy scans behind Č-bar• Mount in any one octant at a time• Attach to fixed support structure• Motion assy mounted “inside” Č-bars

Č-bar

x-axis motion

y-ax

is m

otio

n

Recent Progress on Scanner• 3/06 – Approval from CFI received (detector lab)• 4/06 – Funding from NSERC received (scanner)• Report for today:

– Start of prototyping tests related to detector performance.

– Simulation of detector performance.– Mechanical design

• Mounting and 2D motion assy.• Detector assy.

Prototyping Tests

• 2” tube lined with “Alzak” sheet (aluminum sheet with PVD aluminum on top, and clear anodized)

“Anomet” “MIRO 2”

(Pan, Wang, Harrison)

Prototyping Tests – Cosmics Testing

upper trigger

lower trigger

test detector

inside Alzak tube isa small test scint

mounted on a plunger

Prototyping Tests• MCA reads out

shaped pulse height.

• Begun work with small scintillator samples. (Plan to transition to quartz)

• Begun work with high reflectivity light pipes.

• Electronics to be replaced with CFI funded detector lab.

Simulation

• Builds on QweakSim (K. Grimm, M. Gericke)

• Currently at stage of benchmarking vs. E158 NIM article.

Simulation – comparisons to E158 NIM

• work in progress

• q.e. model not right, etc.

E158 Jie Pan

differentprerad

Mechanics

• support structure (P. Medeiros, G. Smith)

• 2D motion assy.

• detector assy. (P. Wang and G. Mollard @ UM)

Mechanics

• support structure– early 2006, decision to not use R3 rotator– plan now is to mount to fixed Cherenkov-bar support

structure, most of device in towards beamline.– motion octant-to-octant possible by bolting device in

place– need drawings!

• 2D motion assy.– budgetary quote from Bosch-Rexroth.– no progress other than some discussions with P.

Decowski (E158 scanner) on rad hardness.

Mechanics

• detector assy.– initial 2D CAD

drawings– begun 3D SolidWorks

model (P. Wang)– eventually, support from

UM shop (G. Mollard)

starting onSolidWorksdesign

Summary and to-do list• Answer prototyping/simulation questions:

– radiator design (quartz? scint? size? tilt angle? prerad?)

– tube diameter (backgrounds)

– two-tube layout (backgrounds and fiducial area)

– establish viability of coincidence technique (rates)

• Mechanics– support structure – need P. Medeiros’ time.

– purchase 2D motion assy. and program it.

– design and build a mechanical mock-up of detector assy and then a realistic detector

Additional Usesof a Scanner Detector

• Scan over large fiducial region, into inelastic region, over Cherenkov bar light guides, to get additional confidence in backgrounds.

• “Light map” can be compared to simulation.• Q2 extrapolation/determination

– mini-torus setting during production running?– gas vs. liquid target extrapolation?– at least, complementary to region III.

Implementation in Qweak

• 2D motion assy scans behind the Č-bar• Mount in one octant, attach to fixed support

structure

Č-bar

x-axis motion

y-ax

is m

otio

n

Implementation in Qweak

Implementation in Qweak

Implementation in Qweak

Implementation in Qweak

• Expected rates at 180 A

• Max rate = 1 MHzcourtesyJ. Mammei

Procedure• Measure light distribution with scanner at

low beam current acceptable to region III and Cherenkov bar coincidence.

• Measure light distribution with scanner at 180 uA.

• If they are the same, region III/Cherenkov light distribution believable at 180 uA to high confidence.– Note: scanner light map will not be the same as

the region III/Cherenkov bar coincidence map.