1. Slides/Talking Points for October 2007 Consortium Meeting
C. Darren Dowell
Draft: October 17

2. Topics Microphonics characterization plans Photometer PCAL response
Spectrometer PCAL response
High flux mode for photometer
Simpler approach to Section in Pipeline document

3. SPT Microphonics Characterization: Minimal Approach
Photometer:
Quiet bias frequency settings from PFM5 (to demonstrate good SPIRE performance): Hz
Noisy settings from PFM5 (which are most sensitive for “accelerometery”): Hz, Hz
Spectrometer:
Quiet settings from PFM5: Hz
Noisy settings from PFM5: Hz

4. Photometer Microphonics

5. Spectrometer Microphonics
Note change of scale from photometer microphonics. SLW is similar to photometers.

6. SPT Microphonics Characterization: Thorough Approach
Many features apparently enter the system at higher harmonics of the demodulation frequency (=bias frequency).
Since the demodulation is square wave, the low odd harmonics are relevant.
Given the 5 (24) Hz post-demodulation bandwidths of the photometer (spectrometer):
Bias frequency searches stepped by 5 (24) Hz only find all of the first harmonic microphonics.
New features from higher harmonics could appear at in-between frequency settings.
Searches stepped by 1.6 (8) Hz find all of the third harmonic features, etc.

7. “Proof” of Higher Harmonics
(Include a plot here)

8. PCAL Photometer Calibration
PCAL response follows trend to ≤5% precision.

9. PCAL Photometer Calibration
Bolometer model is fairly good at recovering the PCAL power regardless of detector conditions (SUBKTEMP).

10. PCAL&SCAL Spectrometer Calibration
Data analysis to do…
Hopefully a demo that base temperature drifts and loading changes both follow the same curve of responsivity vs V(detector).

11. High Flux Mode for Photometer
The typical photometer pixel readout saturates at 200, 360, 310 Jy/beam for 200, 350, 500 m, but interesting regions of the Galaxy are brighter than this. (Especially a problem at 200 m.)
References:

12. Three Solutions Decrease bias to decrease responsivity:
Responsivity can be made arbitrarily small
Significant variation from pixel to pixel
Maximum flux nonlinearity
Increased NEP
Enhanced microphonic, temperature fluctuation, and bias fluctuation sensitivity
Thermistors usable
Increase bias to decrease responsivity:
Factor of 3 decrease possible (90 mV vs. 15 mV)
Low flux nonlinearity
Lowest temperature fluctuation sensitivity
Thermistors saturate  no temperature drift correction
Raise detector operating temperature to decrease responsivity:
Factor of 3 by going from 310 mK to 420 mK
Increase NEP
Best solution? Fixed heat on charcoal pump? However, slow to switch normal  high flux modes.
References:

13. High Flux Mode for Photometer
Whatever the high flux mode is, it needs its own set of calibration tests:
PCAL responsivity with the new bias + range of loading
Temperature drift correlations
Transfer function
References:

14. Calibration Strategy See Pipeline document, Section 4.2.6, option 2
The “linearized voltage” idea I proposed didn’t catch on.
Still, I think this section could be improved. Hopefully I’ll have a draft to review.