Plans for Radiation Damage Studies for Si Diode Sensors Subject to GRaD Doses International Linear Collider Workshop University of Texas at Arlington October 22-26, 2012

2 The Issue: ILC BeamCal Radiation Exposure ILC BeamCal: Covers between 5 and 40 miliradians Radiation doses up to 100 MRad per year Radiation initiated by electromagnetic particles (most extant studies for hadron – induced) EM particles do little damage; might damage be come from small hadronic component of shower?

3 Damage coefficients less for p-type for E e- < ~1GeV (two groups); note critical energy in W is ~10 MeV But: Are electrons the entire picture? NIELe - Energy 2x MeV 5x MeV 1x MeV 2x MeV G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993)

LCLS and ESA Use pulsed magnets in the beam switchyard to send beam in ESA. Mauro Pivi SLAC, ESTB 2011 Workshop, Page 4

ESTB parameters 0.25 nC ParametersESA Energy15 GeV Repetition Rate5 Hz Charge per pulse0.35 nC Energy spread,  E  /E 0.02% Bunch length rms 100  m Emittance rms (  x  y ) (4, 1) m-rad Spot size at waist (  x,y  < 10  m Drift Space available for experimental apparatus 60 m Transverse space available for experimental apparatus 5 x 5 m

6 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 MeV (~E critical ) Photoproduction Threshold seems to be about 200 MeV Nuclear Compton scattering Threshold at about 10 MeV;  resonance at 340 MeV  These are largely isotropic; must have most of hadronic component develop near sample

7 5.5 GeV Shower Profile Radius (cm) Fluence (particles per cm 2 ) e + e - (x10) All  E  > 10 MeV (x2) E  > 100 MeV (x20) Remember: nuclear component is from photons in MeV range. “Pre” “Post”

Proposal: JLAB Hall B Beam Dump (Plan to run 0.05  A through next May)  Total power in beam ~250W. Oops – too much background for Hall B! What about SLAC? Pre-radiator Post-radiator and sample

9 Hadronic Processes in EM Showers Status: Thermal prototype under testing at SCIPP

10 Proposed split radiator configuration Radius (cm) Fluence (particles per cm 2 ) 5mm Tungsten “pre” 13mm Tungsten “post” Separated by 1m

Rastering Need uniform illumination over 0.25x0.75 cm region (active area of SCIPP’s charge collection measurement apparatus).  Raster in 0.05cm steps over 0.6x1.5 cm, assuming fluence profile on prior slide (see next slide for result) Exposure rate: e.g. 100 MRad at 1 nA 13.6 GeV e -  ~ 5 Hrs

12 Charge Collection Apparatus Need to upgrade CC Apparatus for multiple samples New detector board to modularize system (connector rather than bonds) Two pitch adapters (lithogaphic) to accommodate different detector pitches Modications to ASIC board Design review Monday 12/19 Sensors Sensor + FE ASIC DAQ FPGA with Ethernet

ISSUES/CONCERNS/FEATURES Alignment and Rastoring We’ll need to know the absolute beam location to 1mm or so Will rastoring be available, or will we need to move samples around ourselves? It would be much easier for our design if the beam moved. Radiomtery We’ll need dosimetry at ~10% accuracy Will we need to worry about activation (we plan to do our damage assessment back in Santa Cruz

ISSUES/CONCERNS/FEATURES II Long Running periods (~60 hours for 1 GRad) Can we run parasitically? What access can we have during parasitic running? Infrastructure Temperature control (thermal load from beam ~10W, plus need to avoid annealing), Control systems, etc.

Parameters required for Beam Tests Beam parametersValueComments Particle Typeelectron EnergyMaximum Rep RateMaximum Charge per pulseMaximum Energy SpreadNot a concern Bunch length rmsNot a concern Beam spot size, x-yLarge is helpfulUp to ~1 cm rms Others (emittance, …)Not a concern LogisticsRequirements Space requirements (H x W x L)  m x 1m x 1m (plus 20cm x 20cm x 20cm 1-2 meters upstream) Duration of Test and Shift UtilizationDepends on available current Desired Calendar DatesCY 2012 (flexible) To the presenter at the ESTB 2011 Workshop: please, fill in the table (at best) with the important parameters needed for your tests

SUMMARY ILC BeamCal demands materials hardened for unprecedented levels of electromagnetic-induced radiation 10-year doses will approach 1 GRad. Not clear if hadrons in EM shower will play significant role  need to explore this At 1 nA, 1 GRad takes a long time (60 hours); multiply time ~10 samples  really long time More beam current (?) Start with 100 MRad studies (already interesting)

Backup

18 Shower Max Results  Photon production ~independent of incident energy! Electrons, per GeV incident energy Photons per electron Photons with E > 10 MeV per electron, x10 Photons with E > 100 MeV per electron, x 100

19 Damage coefficients less for p-type for E e- < ~1GeV (two groups); note critical energy in W is ~10 MeV But: Are electrons the entire picture? NIELe - Energy 2x MeV 5x MeV 1x MeV 2x MeV G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993)

GeV Shower Profile Radius (cm) Fluence (particles per cm 2 ) e + e - (x10) All  E  > 10 MeV (x2) E  > 100 MeV (x20) Remember: nuclear component is from photons in MeV range. “Pre”“Post”

mm from center Fluence (e - and e + per cm 2 ) per incident 5.5 GeV electron (5cm pre-radiator 13 cm post-radiator with 1m separation) ¼ of area to be measured Center of irradiated area ¼ of rastoring area (0.5mm steps)

GeV Electrons After 18mm Tungsten Block Radius (cm) Fluence (particles per cm 2 ) Boundary of 1cm detector 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!

23 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 E c Tungsten ~ 10 MeV, NIEL is 80 times worse for protons than electrons and NIEL scaling may break down (even less damage from electrons/positrons) NIEL rises quickly with decreasing (proton) energy, and fragments would likely be low energy  Might small hadronic fractions dominate damage?

24 e +/ e - ENERGY (GEV) BeamCal Incident Energy Distribution

25 Wrap-up Worth exploring Si sensors (n-type, Czochralski?) Need to be conscious of possible hadronic content of EM showers Energy of e - beam not critical, but intensity is; for one week run require E beam (GeV) x I beam (nA) > 50 SLAC: Summer-fall 2011 ESA test beam with E beam (GeV) x I beam (nA)  17 – is it feasible to wait for this?

26 Rates (Current) and Energy Basic Idea: Direct electron beam of moderate energy on Tungsten radiator; insert silicon sensor at shower max For Si, 1 GRad is about 3 x /cm 2, or about 5 mili-Coulomb/cm 2  Reasonably intense moderate-energy electron or photon beam necessary What energy…?

27 Proposed split radiator configuration Radius (cm) Fluence (particles per cm 2 ) mm Tungsten “pre” 18mm Tungsten “post” Separated by 1m

28 Illumination Profile Uniform to  10% over (3x6)mm area