CSCM: The measurement cycles (at least the one for the RB)

1. CSCM:The measurement cycles(at least the one for the RB) Arjan Verweij 12 may 2011

2. T=20 K (error to be defined) I tplateau Iplateau Typical cycle Fast ramp down if V>Vthr dI/dt FPA if V>Vthr dV/dt to open the diodes t1 t2 t Arjan Verweij 12 may 2011

3. Dynamic threshold for QPS is needed Vthr has to be defined so that: Peak temperature during thermal runaway remains below 300 K Vthr > VR,bus(t=t1)+Vind,bus Vthr > VR,bus(t=t2) VR,bus is linear to the length of the measured bus segment and to the plateau current Vind,bus is linear to the length of the measured bus segment and to the dI/dt at 1000 A/s: Vind=20 mV (for 30 m bus) Vthr probably has to be set to different values for each bus segment, and will increase for higher currents. The longer bus segments towards the DFB’s are the most critical. Arjan Verweij 12 may 2011

4. RB, 30 m, 6 kA, 40 mm defect, RRRdefect=120, RRRbus=200 Vthr Dt between threshold and T=300 K is about 0.26 s VR+Vind at t=t1 Arjan Verweij 12 may 2011

5. RB, 30 m, 6 kA, 40 mm defect, RRRdefect=120, RRRbus=200 Arjan Verweij 12 may 2011

6. The tests Test at 1000 A: general check of all signals. Define V0 and RRR of all the bus segments. After this test the thresholds can be defined. Test at 4500 A: find the very large defects (50-100 mW) without the risk of a very fast thermal runaway. If no defect found at 4500 A then: Test at 6000 A: find defects of the order of 30-50 mW. 2nd test at 4500 A/6000 A: ensure that the thermal runaway did not deteriorate the defect Assuming bus of 30 m, RRR=200, neglecting ramp up and ramp down. LRB=4 mH Arjan Verweij 12 may 2011

7. Bus segments are 100 m (and some up to 260 m) instead of 30 m. Bus segments have smaller cross-section.  Maximum dI/dt has to be set lower (about 300 A/s).  Plateau time has to be shorter RQ Assuming bus of 100 m, RRR=200, neglecting ramp up and ramp down. LRQ=4 mH Arjan Verweij 12 may 2011

8. RQ, 260 m, 4.5 kA, 40 mm defect, RRRdefect=120, RRRbus=200 Voltage increase of the bus larger than voltage increase due to thermal runaway. To be avoided!!!!!! Arjan Verweij 12 may 2011

9. A critical defect for 5 TeV operation can be found with safe thresholds, data acquisition sampling, etc., with probably 4 tests (1 kA, 4.5 kA, 6 kA, 6 kA). Due to the longer section towards the DFB (52 m) we might have to reduce the ramp rate (no big problem) and possibly increase the threshold a bit, but this will still be safe. We can probably manage to perform all tests with only a few thresholds, depending on: • Length bus segment: 32, 38, 52 m : 1, 2, or 3 settings • RRR of the bus segment: 150-300 : 1 or 2 settings • Plateau current: 1, 4.5, 6 kA : 3 settings Conclusion RB Arjan Verweij 12 may 2011

10. Dynamic threshold setting is crucial because the entire bus segment voltage rises more quickly. The long sections towards the DFB (260 m) are the bottleneck. Probably more tests are needed with shorter plateau time: e.g. 1 kA-60s, 3 kA-60s, 4 kA-30, 4.5 kA-20s, 5 kA-15 s, +1 repeat test. Still much more modeling and thinking is needed…… (estimate: a few months full time) Conclusion RQ Arjan Verweij 12 may 2011

11. Annex: Diode opening Arjan Verweij 12 may 2011