PhD Thesis -- TWIST Hardware
-RPM 06.11.07

CHAPTER COMMENTS:

There have been a number of improvements to the hardware since
previous rounds; that's probably what I should focus on.  Still need
to describe all the Important Bits, of course, but at just enough
detail to follow the analysis and systematics studies.  (Remember
forward references to the Systematics chapter in Appropriate Places.)

Should the beamline info go here, or in another section?  Probably
just here; the details aren't that important to rho or delta, afaik,
so I can likely get away with just a cursory description of where we
get our muons (and what "surface muon" means) and what else other junk
is in the beam.

How much detail I go into in the t0 section (particularly wrt MC
tests) will depend on what I find.  If I see interesting quadratic
structures and such, I'll need to show them so they'll make sense in
the corresponding Systematics section.

OTOH, it's probably important to show representative TDC spectra from
data and MC, to show that the leading edges match well and the MC t0
measurement is meaningful.

Actually, I can reference the TWIST NIM paper for a lot of this.  I
should skim that and see what's in it, so I know what I can reference
there.  For this chapter I want to keep it to the minimum the reader
needs to understand everything else.

Does Blair's thesis have info on hardware improvements?  Or does he
just describe things as they were in 2004?

The TEC section can be pretty brief, mainly since I'm not especially
sensitive to the beam profile.


CHAPTER OUTLINE:

- Overview

  - Show figure!

  - Core of TWIST is a symmetric stack of high-precision tracking
    chambers.

    - Polarized muons are stopped in a target at the centre.  Decays
      are tracked and their momentum and angle are reconstructed.

    - Low mass reduces scattering and eloss, and allows the muons to
      reach the centre even at these low energies.

    - Strong 2 T magnetic field fixes the muon polarization in the
      face of scattering in the detector; muons encounter no material
      until they're well inside the field.

  - Brief overview of the chapter.  

- Beamline overview

  - Proton beam and production target

  - M13

    - Beamline elements

      - Slits and jaws control rate and shape

      - Improved control software and readback (?) (*NEW*)

        - I think the dipole stabilizers were used for the first time
          in 2004.

    - Momentum selection will impact stopping distribution, important
      for both rho and delta.

    - Beam contents

      - cite my MSc thesis!  because I can! *g*

      - Describe CPTOF.

    - Edge scan description.

      - Edge scan uses surface muon cutoff to calibrate momentum and
        dp/p of the beamline.

      - Show plot.  (Probably my own.)

    - Muon beam monitor

      - Describe the TEC in brief.  Cite TEC paper.

        - Should probably have a simple diagram of some sort.

      - Profiles taken for each set.

- TEC (*NEW*)

  - Briefly describe the overall design and location.  Mention low
    pressure etc.  Reference the TEC paper for details.

  - Separate X and Y modules.  Should have a diagram of a module, I
    suppose.

  - Drift times allow measurement of track location in each wire cell,
    giving position vs Z through the chamber -- provides position and
    angle information for the track.

- Detector overview

  - Detector coordinate system

  - Magnet

    - Superconducting solenoid inside steel yoke

    - Field very uniform (quote uniformity level)

    - Opera simulation of field used for analysis and MC; accuracy
      checked with field map

    - Field map scaled to NMR probe readings

  - Gas degrader

    - Automatic adjustments by Slow Controls to maintain constant
      stopping distribution (*NEW*) 

  - Trigger

    - M = M1+M2

    - Alternate triggers for other uses (MLT, MTEC, PU, DS)

  - Chambers

    - Foil planes and wire planes

      - Need diagrams:

        - Wire plane orientation

        - Side view of the detector [done]

      - Now instrumenting the full Dense Stack! (*NEW*)

      - Precision of wire placement (by hand, by yours truly!)

      - Asymmetric construction

      - Bulges

      - Online monitoring (*NEW*)

    - Citals for Z locations

      - Now accounting for exact cital sizes in simulation and
        analysis (*NEW*)

    - DCs vs PCs

      - Mention Dense Stack

    - Pre-amps (VTX), post-amps, and FastBus TDCs (see Jim's thesis,
      p.35)

    - DC STRs

    - TEC

  - Stopping target  

    - Mention support structure, kapton masks, etc.  Diagram would be
      useful.

    - Point out the much better knowledge of the aluminum target vs
      the graphite/mylar one.  (*NEW*)

      - We still avoid using the region with the kapton masks etc.

- Control software (integrate with above sections, don't need to
  describe separately...)

  - Misc control software (EPICS, Tcl)

  - DAQ

    - MIDAS, on Linux

  - Slow controls

    - with interface to MIDAS

- Calibration

  - Alignment

    - Rough overview of alignment techniques.  Don't need much
      details, since I didn't have anything to do with this side of
      it; this'll probably fit in a couple of paragraphs.

      - Now using 44-plane alignment! (*NEW*)

      - Investigate whether the B-field alignment was used at all for
        the 2002 analysis.  (*NEW*)

    - Final alignment precision (trans, rot, B-field).

  - t0

    - Rough overview of technique.  Again, keep it brief.  (***Was
      this technique improved between the two analyses?)

    - Include MC and data TDC spectra, emphasizing leading edge shape,
      since we're using MC to get the t0 systematic for data.