Alignment for High Luminosity

Muon Upgrade Meeting
CERN, 24-AUG-09

Kevan Hashemi
Physics Department
Brandeis University


Detector Integration
Radiation Background
Sensitivity to Neutrons
Temperature and Dark Current
Temperature Compensation
Neutron Dosimeter
Ionizing Dose
Rad-Hard Light Sources

Detector Integration

Phase One Upgrade of End-Cap Small Wheel:

Phase Two Upgrade of End-Cap Small Wheel:

Main contacts at Brandeis for Integration Work:

Radiation Background

Motivation for Radiation Studies:

Propose to use alignment system to measure Phase Zero background:

Sensitivity to Neutrons

  • MOUON-98-253, 1998
  • MOUON-2000-011, 2000
  • Dark current increased linearly with time.
  • Sensors L2 and L4 at closer range.
  • Sensors L1 and L3 at farther range.
  • 1 Tn = 1012 1-MeV eq. n/cm2.
  • Max simulated end-cap dose 0.8 Tn.
  • Alignment system tolerates 4 counts/ms.

Temperature and Dark Current

  • Neutron damage heals rapidly at 200°C (L4).
  • After 200°C bake, no further healing (L4).
  • Neutron damage heals slowly at 20°C.
  • Dark current drops 10% in 1 yr.
  • Dark current drops 60% in 11 yrs.
  • Healing raises our radiation tolerance.

Temperature Compensation

  • I = βD eαT
  • I is dark current
  • D is neutron dose
  • α = 0.082 /°C
  • β = 0.41 counts/ms/Tn
  • Ignores anealing
  • I doubles every 8.5 °C

Neutron Dosimeter

Ionizing Dose

Rad-Hard Light Sources

Light sources without electronics provide better tolerance to radiation.

Device Resolution (μm)
BCAM Laser Diodes 0.24
Retroreflective Corner-Cube 0.28
Plastic Light Pipe Diameter 250 μm, Length 1.7 m 0.59
Plastic Light Pipe Diameter 250 μm, Length 5.8 m 0.34
Retroreflective Tape 1.9
Single Mode Fiber 0.74
Table: Light Source Performance at Range 1.5 m

Unable to obtain adequate images with steel ball reflectors at 1.5 m.

Optical fiber is radiation resistant and provides good resolution.

Must figure out an inexpensive way to couple laser light into fibers.

Plastic light pipes easier to couple to laser, but may not be rad-hard.

Our current work in Light Sources report on BCAM Home Page.


  1. Brandeis committed to coordinating integration of new detectors.
  2. Brandeis committed to building new alignment systems for new detectors.
  3. Hope to measure neutron dose to 0.002 Tn or 2%, whichever is greater.
  4. Max end-cap simulated dose per year is 0.08 Tn.
  5. Investigating using logic circuit current to measure ionizing dose.
  6. Investigating various new BCAM light sources.
  7. Light sources made with optical fibers would be rad-hard.