MultiChannel Electronics SCUBA 2 MCE 4 readout cards

Multi-Channel Electronics

SCUBA 2 MCE • 4 readout cards (RC) – each reads 8 output columns through 14 -bit 50 MHz ADCs • 1 address card (AC)= SQ 1_bias – addresses the [41] rows at add ≤ 850 k. Hz, set by L/R – frame ≤ add /41≈ 20 k. Hz • 1 clock card (CC) – master card: interprets commands and synchronizes all the cards. Drives fibre to PC. • 3 bias cards (BC) – BC 1: Squid Series Array Feedback (x 32) + TES bias(x 1) – BC 2: Squid 2 feedback (x 32) – BC 3: SQ 2 bias(x 32) + TES heaters(x 1)

SPIDER MCE • SPIDER (as well as SPUD and BICEPII) have up to 33 rows and 16 columns for each array • Repackaged MCE: – 2 RC’s – Reorganized BC’s duties • Additional features: – More DET_BIAS (already in place) – SQ 2_fb fast switching (to achieve a better lock and to remove summing coil pickup switching off all SQ 1_bias and adjusting SQ 2_fb. However with fixed values. Or we could effectively connect the dark SQ sq 1_fb with the sq 2_fb)

Cards in SPIDER MCE • 3 BC’s • • BC 1 0/16 SSA_fb, 0/16 SQ 2_BIAS, DET_BIAS_ORG BC 2 0/16 (possibly fast switching) SQ 2_FB BC 3 0/16 DET_BIAS In the current configuration slow SQ 2_FB and 16 DET_BIAS slightly different from DET_BIAS_ORG • 2 RC’s • RC 1 0/7 SQ 1_FB, 0/7 SSA_BIAS • RC 2 8/15 SQ 1_FB, 8/15 SSA_BIAS • 1 AC, 1 CC

Subrack in SPIDER MCE T Felton design

Backplane in SPIDER MCE SQ 1_fb: it was 450 A, now 150 A because of the increase in the mutual inductance of MUX 06. Is it fine? DET_BIAS: the maximum we can achieve now is 4 m. A. It can be increased. Should it?

PSU in SPIDER MCE • Power supply: – We currently use an ACDCU with a switching power supply – For SPIDER: • we may use batteries – 119 W for SCUBA 2. For SPIDER: 16 columns 73 W (23 W each RC)

Cooling SPIDER MCE • Cooling: – We currently use fans and filtered air with positive pressure to the gondola frame, used as heatsink – SPIDER MCE will be radiatively cooled using circulating fluid with a pump T Felton design

SEU in SPIDER MCE • Cosmic rays on FPGA and SEU tolerance: 1 per month at JCMT ~1 SEU / board / LDB flight. We are already in contact with the TRIUMF particle accelerator for realistic neutron fluency test (in fact, test flight would not reveal the real effect). • Altera Stratix III FPGA’s offer additional on chip monitoring and testing features wrt Stratix I. We would not use it for the test flight. Maybe for SPIDER. • PC’s in pressure vessel (HD). Two with crosscomunication. • The syncbox could be there as well.

Schedule for SPIDER MCE • For the new repackaged MCE with no cards redesign: – – – Finalize the design 1 -2 weeks Backplane 6 -8 weeks Chassis our machine shop, 6 weeks New FPGA? Probably not for the test flight. Maybe for SPIDER Cooling system 4 -5 weeks New filter box and flex (rigid-flex, 1 connector less, and no ground plane) 6 -8 weeks – Test 6 -8 weeks – SEU test ? – New boards new year

Modulation schemes – TES bias – SQ 1 fb (switching) – SQ 1 fb (ramping)

TES bias – The TES bias could be square (or sine) wave modulated at ~1 k. Hz. We have the firmware for s. w. that can run as fast as half the framerate – However, if the bias crosses zero for more than few hundreds s, than the TES’ may not recover Superconducting branch Superconducting transition Acquired on the ACT CCam camera Normal branch

TES bias – In any TES bias modulation scheme we need a firmware that has to run two separate servo loops. Synchronization is needed. Major firmware change for the read-out and the demodulation. – It can be tested in software since we can already acquire fast data at 2. 2 k. Hz (33 rows, 32 GB/h), 26 k. Hz (1 row). We’d need bolometers to do tests. Acquired on the ACT MBAC camera

TES bias – In any TES bias modulation scheme we need a firmware that has to run two separate servo loops. Synchronization is needed. Major firmware change for the read-out and the demodulation. – It can be tested in software since we can already acquire fast data at 2. 2 k. Hz (33 rows, 32 GB/h), 26 k. Hz (1 row). We’d need bolometers to do tests.

SQ 1 bias modulation – We visit the SQ 1 at up to 20 k. Hz with RS on bias. We could select 2 different on bias’ and switch at sub-harmonics of 20 k. Hz. – The firmware demodulation (i. e. remove off from on) would be straightforward since it would be a modification of the coadding we already implement. Acquired on the ACT CCam camera

SQ 1 bias modulation – We visit the SQ 1 at up to 20 k. Hz with RS on bias. We could select 2 different on bias’ and switch at sub-harmonics of 20 k. Hz. – We could invert the polarity of the SQ 1_bias (although now it is not bipolar) and keep the same inverted polarity lock point. Acquired on the ACT CCam camera

SQ 1 fb modulation (switch) – The SQ 1_fb could be switched so that the PID feedback loop works in opposite SQ 1 slope – A firmware should be created that enables opposite locking. That could be done with I-term=I·(-1)#frames except that it would take time – However it should require a fine tuning and … Acquired on the ACT CCam camera

SQ 1 fb modulation (switch) – The SQ 1_fb could be switched so that the PID feedback loop works in opposite SQ 1 slope – A firmware should be created that enables opposite locking. That could be done with I-term=I·(-1)#frames except that it would take time to relock – However it should require a fine tuning and any asymmetry of the SQ 1 V-phi doesn’t help Acquired on the ACT MBAC camera

SQ 1 fb modulation (switch) – The SQ 1_fb could be switched so that the PID feedback loop works in opposite SQ 1 slope – A firmware should be created that enables opposite locking. That could be done with I-term=I·(-1)#frames except that it would take time to relock – However it should require a fine tuning and any asymmetry of the SQ 1 V-phi doesn’t help a combination of SQ 1_bias and SQ 1_fb modulation so that there are 4 different locking points and/or we keep the same lock point as K. Irwing suggested.

SQ 1 fb modulation (ramp) – We throw away the PID feedback loop and we continuously ramp the SQ 1_fb. This creates an effective modulation of the signal coming form the SQ 1 V-phi curves – We already have a data mode that ramps the SQ 1 fb. In the 14 bits DAC each step can be as high as 10 k. Hz – We look forward to test in software on a system with TES Acquired on the ACT CCam camera