Row-specific SQ2 feedback (fast switching)

The SQ2-Feedback (SQ2FB) output of the MCE, controlled by a DAC can be set to either a constant value or a row-specific set of values switching at row-visit rate. The SQ2FB output is driven by the card plugged into the BC2 slot of the MCE. Either a Bias Card or an Address Card can be plugged into the BC2 slot.

Bias-card-driven SQ2FB

Prior to Rev. F

Bias Cards earlier than Rev. F have a slow opamp at the output followed by 2 sets of kHz range RC filters that limit the output switching frequency to few kHz range and prevents the output from switching at the row-visit rate. Therefore, when these bias cards are used in BC2 slot, only a constant SQ2FB value (one value per array-column) can be specified.

• Relevant mce parameters
  • flux-fb

Rev. F and later

Bias Cards Rev. F and later have faster outputs and they can be switched at row-visit rate. The firmware support for switching SQ2FB values at row-visit rate is added starting revision 5.0.5.

Relevant mce parameters

fb_col0, fb_col1, ..., fb_col31 : each specify up to 41 values, loaded in order when enbl_mux is set to 1

enbl_mux : 0 to have constant outputs, 1 to have switching ouputs

flux_fb  :

row_len  : specifies output switching rate

Software requirements

Address-card-driven SQ2FB

http://cmbr.phas.ubc.ca/mcewiki/index.php/Fast_SQ2_Feedback_and_TES_Biasing_with_an_Address_Card

detector bias considerations

Firmware requirement

v5.0.0+

Software requirement

Edit experiment.cfg file to set

 hardware_bac=1
 config_fast_sq2=1