Main Detector Status March 06

1
Main Detector Status (March 06)
D. J. Mack (TJNAF) Qweak Collaboration meeting at
JLab March 10, 2006

• requirements
• status
• upcoming work
• summary

2
Requirements
Neven Simicevic (LaTech) did the original Qweak
simulations assuming a reconfigured G0 torus
which focused the elastic electrons onto rad-hard
Cerenkov radiators read out by PMTs with S20
photocathodes. Over 5 years, some of the details
have changed (eg, G0 ? QTOR), but not so many!

• Isolates elastic ep? ep
• Close to counting statistics
• Insensitive to backgrounds
• Insensitive to rad. damage
• Modest Q2 bias
• Nonlinearity of less than 1
• Switchable between
• current-mode (PV production)
• and
• pulsed-mode (bkg studies)

and non-pathological sensitivities!
3
Present Design
Elastics fit on the bar and are consistent with a
final error on Qweak(p) of 4. (Hard work!)
200 cm x 18 cm x 1.25 cm
The shield house window is a hard aperture that
we have to shoot thru with perhaps -2 cm
tolerances. (Thats a percent or two in B-field.)
We need to get thru the window cleanly, adjust
the field to optimize the background, then leave
the field alone. If we want to move the envelope
on the quartz (to check Jim Birchalls models,
for example), we need to move the quartz.
Shield house window and wall in progress. See A.
Opper talk (GWU).
4
Fused Silica Radiators
First articles have arrived! 4 of 19 bars each
100 cm long No detailed QA yet, but quality looks
good. (recall 19 bars are sufficient for 8
complete detectors, 1 complete
background/spare detector, and a single spare bar)

• Work by collaborators established the final
  dimensions of
• 200 cm x 18 cm x 1.25 cm

Greg Smith found us a nice place to keep stuff!
Delivery of last shipment of bars will be delayed
until August to allow manufacturer to make
changes to reduce chipping and increase his
yields. Everyone is happy with that.
5
Detector Module Misc.

• All PMTs are on-hand and tested.
• All magnetic shields are on-hand.
• Need lightguides and bases!

Radiator is upstream of its supporting frame.
PMT with magnetic shield, showing attachment lugs
to socket ears.
6
Expected Performance I
Systematic Performance (J. Birchalls
Sensitivities)
Statistical Performance (Des Ramsays
noise estimates)
7
Expected Performance II
8
Upcoming Tasks

• Fab (goal main detector wont hold up
  installation schedule)
• Finalize prototype design.
• Manufacture parts for summer assembly.
• Cosmic tests on prototype summer 06
  (scintillation and luminescence too)
• Complete all 81 modules by end of summer 07.
• Bkg (goal good planning now, or eat shit and
  die when the beam comes on)
• Working with GWU to get rid of 1-bounce bkgs and
  optimize shield house window.
• Following VPIs beamline background work with
  great interest
• Fall 06 field test of JLab 250 MHz transient
  digitizers for unbiased bkg studies
• Longer term how to measure photon bkgs (NaI?)
• Sims and Ancillary tests (goal understand the
  apparatus)
• Q2 bias and evolution wrt rad damage,
• linearity and noise tests with 5-stage base,
• field test TRIUMF 50 KHz sampling ADC prototype
  for parity DAQ,

9
Related Talks at this Meeting

• Main detector
• TRIUMF low noise electronics Des Ramsay
• Lightguide Sims Michael Gericke
• Backgrounds
• Elastic channel EM backgrounds/shielding
  Allena Opper
• Beamline EM backgrounds/shielding Juliette
  Mammei
• Preradiator Sims (Plan B) Michael Gericke

10
Recent Related Reports

• WBS1 (Main Detector and Electronics)
• How Should We Calculate the Asymmetry of a Single
  Bar?
• Qweak 526-v1
• Irradiation Test of TRIUMF Preamplifier Qweak
  529-v1
• Selection of Lightguide Geometry Qweak 533-v2
• Draft Lightguide Specifications Qweak 537-v1
• Diode Mode Linearity Tests Qweak 534-v1
• WBS6 (Infrastructure)
• Elastic Channel Background Studies I (Lintels)
  Qweak 536-v1

11
Summary

• Entering peak main detector construction phase.
• Qweak WBS1 manpower totals 2.5 physicist FTEs,
  including a fraction of Qweaks sim experts. Two
  of us have significant G0 responsibilities, and I
  am trying to help out with beamline diagnostics
  and shielding issues. Offers of undergrad summer
  students are very welcome, but we need graduate
  student participation to ramp UP not DOWN.
• No one has ever put together an experiment like
  this before. It will only succeed if we execute
  good designs and fully understand our apparatus.
  Work that our students and postdocs do now will
  affect the outcome! Our to-do list contains
  amazingly cool projects that will give students
  great experience to further their careers as
  experimental physicists!