Focal Plane Scanner Jeff Martin University of Winnipeg with: Jie Pan, Peiqing Wang, David Harrison

Motivation Q 2 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 cm 2 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-core light pipe quartz radiator pre-rad

Scanner Concept scattered electrons 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-axis motion

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 is a 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 different prerad

Mechanics support structure (P. Medeiros, G. Smith) 2D motion assy. detector assy. (P. Wang and G. 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 on SolidWorks design

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 Uses of 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. Q 2 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-axis motion

Implementation in Qweak

Expected rates at 180  A Max rate = 1 MHz courtesy J. 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.