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Entry  Thu Aug 20 00:21:51 2020, gautam, Update, Electronics, First look at HV coil driver IMG_8724.JPGtimeDomain.pdfHVampNoise.pdf
    Reply  Sun Aug 23 23:36:58 2020, gautam, Update, Electronics, First look at HV coil driver IMG_5379.JPGstabilityCriterion.pdf
       Reply  Wed Aug 26 16:12:25 2020, gautam, Update, Electronics, Test mass coil current requirements coilCurrents.png
       Reply  Tue Sep 1 15:39:04 2020, gautam, Update, Electronics, HV coil driver oscillations fixed testSetup.pdfHVampNoise_driven.pdf
          Reply  Thu Oct 22 11:14:47 2020, gautam, Update, Electronics, HV coil driver packaged into 2U chassis HVampNoise_driven_chassis.pdfHVampNoise_dispUnits.pdfD1900163_measurementSetup.zip
             Reply  Thu Oct 22 13:04:42 2020, rana, Update, Electronics, HV coil driver packaged into 2U chassis 
                Reply  Thu Oct 22 22:01:53 2020, gautam, Update, Electronics, HV coil driver packaged into 2U chassis DACnoiseFilterGain.pdfDACnoiseFilterNoises.pdf
                   Reply  Fri Oct 23 09:03:43 2020, anchal, Update, Electronics, HV coil driver packaged into 2U chassis 
             Reply  Thu Nov 12 14:55:35 2020, gautam, Update, Electronics, More systematic noise characterization powerSupplyNoise.pdfcoherence.pdf
                Reply  Thu Nov 12 15:40:42 2020, Koji, Update, Electronics, More systematic noise characterization 
                   Reply  Mon Nov 16 00:02:34 2020, rana, Update, Electronics, More systematic noise characterization 
                      Reply  Wed Jan 20 10:13:06 2021, gautam, Update, Electronics, HV Power supply bypassing bypassCaps.pdfIMG_9079.jpgIMG_9078.jpgHVampNoise_driven_chassis.pdfprintCoilCurrents.pdf
                         Reply  Mon Feb 1 12:30:21 2021, gautam, Update, Electronics, More careful characterization HVPS.pdfHV_testckt.pdftotalNoise.pdf
                         Reply  Wed Feb 10 21:14:03 2021, gautam, Update, Electronics, Production version of the HV coil driver tested inputDiffRecTF.pdfLVnoises.pdftotalNoise.pdftimeDomainTests.pdf
                            Reply  Fri Feb 26 16:31:02 2021, gautam, Update, Electronics, Production version of the HV coil driver tested with KEPCO HV supplies totalNoise_KEPCO.pdf
                               Reply  Fri Feb 26 20:20:43 2021, Koji, Update, Electronics, Production version of the HV coil driver tested with KEPCO HV supplies 
                                  Reply  Sat Feb 27 17:25:42 2021, gautam, Update, Electronics, Production version of the HV coil driver tested with KEPCO HV supplies 
                                     Reply  Thu May 20 16:56:21 2021, Koji, Update, Electronics, Production version of the HV coil driver tested with KEPCO HV supplies P_20210520_154523_copy.jpg
Message ID: 15534     Entry time: Thu Aug 20 00:21:51 2020     Reply to this: 15536
Author: gautam 
Type: Update 
Category: Electronics 
Subject: First look at HV coil driver 

Summary:

A single channel of this board was stuffed (and other channels partially populated). The basic tests passed, and nothing exploded! Even though this is a laughably simple circuit, it's nice that it works.

HV power supplies:

A pair of unused KEPCO BHK300-130 switching power supplies that I found in the lab were used for this test. I pulled the programmable cards out at the rear, and shorted the positive output of one unit to the negative of the other (with both shorted to the supply grounds as well), thereby creating a bipolar supply from these unipolar models. For the purposes of this test, I set the voltage and current limits to 100V DC, 10mA respectively. I didn't ramp up the supply voltage to the rated 300 V maximum. The setup is shown in Attachment #1.

Tests:

  1. With the input to the channel shorted to ground, I confirmed with a DMM that the output was (nearly) zero (there was an offset of ~40mV but I think this is okay).
  2. Used the calibrated voltage source, and applied +/- 3 V in steps of ~0.5 V, while monitoring the output with a DMM. Confirmed the output swing of ~ +/-90 V, which is what is expected, since the design voltage gain of this circuit is 31.
  3. Drove a 0.1 Hz, 500mVpp sine wave at the input while monitoring the output and the Vmon testpoints, see Attachment #2. Note the phasing between input and output, and also the fact that the gain is slightly lower than the expected gain of 31, because there are three poles at ~0.7 Hz, which already start showing some influence on the transfer function at 0.1 Hz.
  4. Noise measurement 
    • The whole point of this circuit is to realize sub 1pA/rtHz current noise to the coil, when it is connected.
    • For this test, no load was connected (i.e. voltage noise was measured at the output of the 25 kohm resistor), and the input was shorted to ground so that the DC value of the output was close to 0 (the idea was to not overload the SR560/SR785 with high voltage).
    • An SR560 preamp with gain x50 (DC coupled) was used to preamplify the signal. This was the maximum gain that could be used with the unit DC coupled, due to the small DC offset. I opted to keep the DC coupling to get a look at the low frequency noise as well, but in hindsight, maybe I should have used AC coupling as we only care about the current noise at ~100 Hz.
    • See Attachment #3 for results. The measurement is close to the model above ~100 Hz

Need to think more about how to better characterize this noise. An estimate of the required actuation can be found here.

Attachment 1: IMG_8724.JPG  2.953 MB  Uploaded Thu Aug 20 01:22:02 2020  | Hide | Hide all
IMG_8724.JPG
Attachment 2: timeDomain.pdf  199 kB  Uploaded Thu Aug 20 01:31:48 2020  | Hide | Hide all
timeDomain.pdf
Attachment 3: HVampNoise.pdf  199 kB  Uploaded Thu Aug 20 11:14:11 2020  | Hide | Hide all
HVampNoise.pdf
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