Current Status and Future Plans of Experimental Breakdown study at CERN 08 April 2014 Tomoko Muranaka

Overview System I (HRR) System II (DC) Fixed Gap System (HRR) Ongoing Exp -BDR vs Puls width -Dark current measurement -BD distribution gap dependence Hardware Issues -Stiffer wire connecting anode -BD switch control -HRR-2 installation -Temperature control system repair -Controller trigger signal Software Issues -Quasi-automated -VIs to be improved for time efficiency and security -VIs for dark current meas. -Scope ctrl and data reading -Power set point control (from XBox) Ordering-Two more switches?-20 electrodes Plantbd Yinon’s request, Temperature dependence, Void etc. -Collab. with Helsinki’s dynamic vacuum study

System I + HRR Current condition – Some software retouches for proper measurements are required to continue BD vs pulse width measurements. – PIC program has been updated to allow the pulse length to be varied, currently the maximum pulse length is 6.7us and the minimum is ~200ns (90%). – Currently using 7.46kOhm bleed resistor for pulse width measurement. To Do – Continue measurements Possible improvements – Gap changes less smoothly due to stiffer wire connecting anode. – To increase the maximum possible pulse length would require a slightly bigger revision of the PIC controller code. – The minimum pulse length is currently limited by the RC time of the bleed resistor and stray capacitance. One of these would have to be reduced to further decrease the minimum pulse length. Information given by Nick

System II Current condition – Dark current measurements have been done by Iaroslava manually. – BD circuit switches controller (transistor) is broken. – Non contact gap measurement works ok. To do – Get ready for measurements! – Temperature control system repair. AlN plate Assembly N2 circulation test – HRR-2 development & installation. Tasks to be filled – If HRR-2 takes longtime, repair the switch controller & improve non contact gap measurement?

Fixed Gap System Current condition – Second pair of electrodes measured with 60um spacer has been removed. Huge damage, Distribution less even (more in center). – Third pair of electrodes have been installed (#6 and #10) and ready to be measured. To do – Find a way to reduce trigger signal noise. Discussions (from Nick) – Possible 60um electrodes deform more than 20um electrodes. – Controller trigger signal problem was also less of an issue with a smaller gap. – Maybe we should stick to 20um electrodes? – Alternatively it could just be related to the large cluster we had.

Future Speculation (Nick) Larger anode for system I  would give increased gap capacitance  more accurate gap measurement. Beta measurement/HRR/gap measurement switch box (we already have the relays). Fast Beta measurement on each pulse with super quick and sensitive CT. (Also easier with larger anode). REALLY SPECULATIVE – hard disk heads travel quickly over a large area only 10’s of nm above the surface… but they use a surface air resistance effect. Hard Disk Drive spark system. Use opposing permanent magnets to repel the ‘Hard Disk Drive Arm’ Anode from the ‘Disk’ Cathode and to counter electrostatic attraction. At the edge of a standard sized disk spinning at 7200 rpm a 1um spot will be passed over in <3ns. A lower BDR further towards the edge of the disk could indicate the timescale of plasma build up. Force [?] Distance [um] Stable point