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Electromagnetic Radiation Hardness for the ILC BeamCal Sensors

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Electromagnetic Radiation Hardness for the ILC BeamCal Sensors. Argonne SiD Workshop Friday, June 4 2010 Bruce Schumm Santa Cruz Institute for Particle Physics. The SCIPP/UCSC ILC R&D GROUP. Faculty/Senior Vitaliy Fadeyev Bruce Schumm. Collaborators Takashi Maruyama Tom Markiewicz

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slide1

Electromagnetic Radiation Hardness for the ILC BeamCal Sensors

Argonne SiD Workshop

Friday, June 4 2010

Bruce Schumm

Santa Cruz Institute for Particle Physics

slide2

The SCIPP/UCSC ILC R&D GROUP

Faculty/Senior

Vitaliy Fadeyev

Bruce Schumm

Collaborators

Takashi Maruyama

Tom Markiewicz

(SLAC)

Students

Spencer Key

Donish Khan

some notes
Some notes:
  • Beam Calorimeter is a sizable project, ~2 m2 of sensors.
  • Sensors are in unusual regime: ~ 1 GRad of e+/e-; 1014 n/cm2 after several years.
  • There are on-going studies with GaAs, Diamond, Sapphire materials (FCAL report, Nov 2009).
  • We’ll concentrate on mainstream Si technology proven by decades of technical development.
  • There is some evidence that p-type Si may be particularly resilient…

3

slide4

Rates (Current) and Energy

  • Basic Idea:
  • Direct electron beam of moderate energy on Tungsten radiator; follow with silicon sensor at shower max
  • For Si, 1 GRad is about 3 x 1016/cm2, or about 5 mili-Coulomb
  • Current scale is A, which points to the 1-5 GeV beam at CBAF (Jefferson Lab, Virginia, USA)

4

slide5

G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993)

NIELe- Energy

2x10-2 0.5 MeV

5x10-2 2 MeV

1x10-1 10 MeV

2x10-1 200 MeV

Damage coefficients less for p-type for Ee- < ~1GeV (two groups); note critical energy in W is ~10 MeV

But: Are electrons the entire picture?

5

slide6

Hadronic Processes in EM Showers

  • There seem to be three main processes for generating hadrons in EM showers (all induced by photons):
  • Nuclear (“giant dipole”) resonances
  • Resonance at 10-20 MeV (~Ecritical)
  • Photoproduction
  • Threshold seems to be about 200 MeV
  • Nuclear Compton scattering
  • Threshold at about 10 MeV;  resonance at 340 MeV
  •  Flux through silicon sensor should be ~10 MeV e/, but also must appropriately represent hadronic component

6

slide7

1mm Downstream of 18mm Tungsten Block

Not amenable for uniform illumination of detector.

Instead: split 18mm W between “pre” and “post” radiator separated by large distance

Caution:nuclear production is ~isotropic  must happen dominantly in “post” radiator!

Boundary of 1cm

detector

Fluence (particles per cm2)

7

Radius (cm)

slide8

5.5 GeV Shower Profile

“Pre”

“Post”

e+e- (x10)

All 

Remember: nuclear component is from

photons in 10-500 MeV range.

Fluence (particles per cm2)

E > 100 MeV (x20)

E > 10 MeV (x2)

8

Radius (cm)

slide9

Possible split radiator configuration

(needs more study)

Boundary of 1cm

detector

6mm Tungsten “pre”

12mm Tungsten “post”

Separated by 2m

Fluence (particles per cm2)

9

Radius (cm)

slide10

No Beam Spread

Beam Spread = 1mm

Radial Fluence Distributions for Differing Sizes of Gaussian Beam Width (x = y)

Beam Spread = 5mm

Beam Spread = 2mm

10

irradiation plan
Irradiation Plan
  • Intend to use existing sensors from ATLAS R&D (made at Micron). Both n- and p- type, Magnetic Czochralski and Oxygenated Float Zone.
  • Plan to assess the bulk damage effects, charge collection efficiency. This will further assess the breakdown on NIEL scaling (x50 at 2 MeV and x4 at 900 MeV) in the energy range of interest.

Sensors

Sensor +

FE ASIC

DAQ FPGA

with Ethernet

11

slide12

Summary

Suggestion that p-type bulk may be more resilient (why?) is intruiguing

Need to think about nuclear component: may be dominant source of damage

Believe we are getting close to configuration that will accurately reflect BeamCal sensor conditions

Initial contacts with JLab made; not dismissed (yet…) Much work to do to set up and execute meaningful test run, but shooting for Dec 2010  a few months.

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slide13

BeamCal Incident Energy Distribution

2

4

6

8

10

e+/e- ENERGY (GEV)

BUT: Most fluence is at shower max, dominated by ~10 MeV e-, e+ and . Why might (?) incident energy matter?

13

slide14

NIEL (Non-Ionizing Energy Loss)

  • Conventional wisdom: Damage proportional to Non- Ionizing Energy Loss (NIEL) of traversing particle
  • NIEL can be calculated (e.g. G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 [1993])
  • At EcTungsten ~ 10 MeV, NIEL is 80 times worse for protons than electrons and
  • NIEL scaling may break down (even less damage from electrons/psistrons)
  • NIEL rises quickly with decreasing (proton) energy, and fragments would likely be low energy
  •  Might small hadronic fractions dominate damage?

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