1. 5th July 00PSI SEU Studies1 Preliminary PSI SEU Studies Study SEU effects by measuring the BER of the link in  /p beams at PSI. Measure the SEU rate as a function of current in PIN diode SEU rate decreases with increasing  SEU occurs in PIN diode. SEU occurs when energy above DORIC threshold is deposited in active region of PIN diode.

2. 5th July 00PSI SEU Studies2 PSI Beams Used p (  ) contamination in  (p) beam <~10%

3. 5th July 00PSI SEU Studies3 Flux Measurements Flux measured with rate in counter with 2mm diameter scintillator attached directly with optical grease to small Hamamtsu PM. Flux corrected for deadtime due to discriminator pulse width (100ns). Flux checked for one run by Al foil activation analysis. Measure 24 Na activity with Ge(Li) counter. Agreed to within 10 %. At low beam intensity we checked rate in small counter with rate in large counter, Consistent with measured beam profile.

4. 5th July 00PSI SEU Studies4

5. 5th July 00PSI SEU Studies5 SEU Analysis(1) For above 30  A there is no measurable BER with beam off.  BER above this value is due to SEU effects. BER decreases with  SEU occur in analogue part of system. Sensitive volume of PIN (350  m diameter, 15  m thick) >> sensitive volume of transistors.  dominant SEU is due to energy above threshold being deposited in sensitive volume of PIN. For the same beam type/momentum the SEU rate scales with luminosity.

6. 5th July 00PSI SEU Studies6 SEU Analysis(2) There is no value of in the range explored for which the SEU rate is zero.  must accept a finite SEU rate in our TTC system. To compare different beam particle/momentum/flux(F) define a SEU cross section as  SEU =BER/F  SEU correlates with  TOTAL Shape of  SEU versus similar for different beam momenta/particle type.

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8. 5th July 00PSI SEU Studies8 SEU Analysis(3) Large  SEU at 300 MeV/c correlates with total cross sections. Other ratios do not scale with  TOTAL Need detailed SEU calculations (Huitenen) to understand results..

9. 5th July 00PSI SEU Studies9 ATLAS Implications(1) Can use this data to predict BER for ATLAS operation at any flux. Convolute  SEU with spectrum –Model #1: pessimistic. Take  SEU from momentum with largest value of  SEU (300 MeV/c). –Model #2: guess. Take average from  at 3 different momenta. –Model# 3: Realistic. Requires detailed simulation (Huitenen) to give prediction of  SEU with momentum.

10. 5th July 00PSI SEU Studies10 SCT Implications. Minimum value of =75  A Pessimistic model gives –  SEU =3 10 -16 cm -2 SCT maximum flux (barrel layer 3) –F= 2 10 6 cm -2 s -1 Predict (worst case + pessimistic model) –SEU = 6 10 -10 s -1

11. 5th July 00PSI SEU Studies11 SEU and Energy Deposition Use simple model for DORIC to relate to minimum energy deposition in PIN to trigger DORIC E min minimum energy to tirgger DORIC (MeV) I PIN mean PIN current I h hysterisis current in DORIC E eh energy required to create eh pair in Si (3.6 eV) e electron charge  0 1/RC time constant of DORIC i/p (10 9 s -1 )

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13. 5th July 00PSI SEU Studies13 Conclusions SEU rates measured at high fluxes. Significant SEU rates expected in ATLAS BER < 10 -9 can be maintained for SCT. BER expected ~ few 10 -10. Acceptable provided frequent soft resets are issued (~ 1 Hz). BER > 10 -9 expected for Pixel detector. Needs study to assess significance of this result (Pixel detector has more robust data format for L1 triggers). Requires calculations from Huitenen to make accurate predictions for ATLAS environment.