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imagerteleconnotes20180523 [2018/05/23 12:23] – created hananyimagerteleconnotes20180523 [2018/05/23 17:20] (current) – hanany
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 ====== Telecon 20180523 ====== ====== Telecon 20180523 ======
  
-Attending: +Attending: Al, Peter, Tom, Roger, Jacques, Shaul, Qi
  
 Notes by : Qi Notes by : Qi
  
-=== Agenda===+=== Agenda ===
  
   * Temperature Stability and effects on responsivity variations   * Temperature Stability and effects on responsivity variations
     * {{::peter_shirron_adr_stability.pptx|Shirron workshop presentation}}     * {{::peter_shirron_adr_stability.pptx|Shirron workshop presentation}}
 +  * {{::sensitivity_vs_frequency_may19th_2018.pdf|noise/band Figure}} and  {{::sensitivity_vs_frequency_may23rd_2018.pdf|Revised noise/band Figure}}
 +
 +=== Notes ===
 +
 +__Noise/band Figure__
 +
 +Proposed Caption: 
 +"PICO polarization sensitivity (left ordinate and vertical bars), and expected RMS polarization signal intensity (right ordinate and lines) on angular scale of ~1 degree. For emission from Galactic synchrotron radiation and dust grain we use levels averaged over 60% of sky (as defined in 'Planck Intermediate Results. XXX.'). The BB amplitude is obtained with primordial B-modes assuming r=0.001 and lensing B-modes."
 +
 +----
 +
 +Al Kogut's e-mail
 +
 +Hi Josquin,
 +
 +Are those units correct?  uK-arcmin is a noise density (map noise
 +with pixels 1 arcmin in diam, hence pixel area 1 arcmin^2).  Dividing
 +this by the beam FWHM in arcmin gives the noise density per beam
 +(uK/beam), which can then be transformed to units Jy/beam using the
 +usual conversion from thermodynamic temperature units to Jy.
 +That would suggest changing the Y-axis labels from Jy/sr to Jy/beam.
 +
 +But that makes it harder to compare between channels, or between PICO
 +and other experiments, since everything on the plot would then be referred
 +to the specific PICO beam widths.  I'd prefer leaving the units Jy/sr
 +and performing the conversion from arcmin pixelization to steradians.
 +This allows simpler interpretation for any choice of beam.
 +
 +Al 
 +
 +----
 +Carlo's e-mail:
 +
 +And another small check, does the synchrotron curve include curvature in the spectral index?
 +
 +If yes ok, if not we could adopt the one which is used in sims, or add another shaded area with that, since it's rather baseline synchrotron modeling at the moment,
 +
 +Carlo
 +
 +=== Notes ===
 +
 +Temperature Stability and effects on responsivity variations (Peter)
 +  * This was from 2007, not much progress was made due to lack of opportunities
 +    * things like better control system could help
 +    * +/-1 ohm sensitivity, which is +/-7 uK; so the data was at noise level, which prevented them doing better at the time
 +  * blue curves is the current in the magnet, exerted to stability, period about 20 mins
 +  * shorter time scale on temperature (red), when currents change direction
 +  * improvement
 +    * better control in ADR
 +  * key question: given responsivity model, what would 20 uK change do?
 +  * **Peter to send raw data of the plot (AI)**
 +  * **Roger volunteers to take charge of this, calculate equivelent signal from this fluctuation (AI)**
 +  * Shaul: can affect responsivity, not just noise. If we were fluctuating a few mK, large signal far beyond we call noise.
 +  * Jacques: how 3K will be modulated; on ground, noise from all sorts of things are dominant, but in space, this source could be dominant in fluctuation 
 +  * T_focalplane and T_ADR
 +    * time constant C/G: focalplane ~30 kg, C is not hard to estimate, but G may be. **Ask Chris Payne to estimate (AI)**.
 +    * Peter: two different time constants, internal of arrays and between ADR and system. Internal time constant of array is also important.
 +  * Planck active T control
 +    * Jacque: Very long time constant, the fluctuation from dilution does not transfer to focal plane; most fluctuations were from cosmic rays
 +    * Shaul: why was active control still useful if time constant was large? **Check with Brandon (AI)**
 +  * The plot is from 4-stage, 4k to low T; 5-stage should outperform with 1K
 +    * Shaul: 1K stage would have its own fluctuation
 +    * Peter: ASTRO-H lab tests with full space instruments, 3 ADR: 2 upper stage + 1.5 K constant. Fluctuation was within 1mK. Two modes, ADR with liquid helium and without helium. Turned out without was more stable, gave better detector resolution, because of more stability under ADR; with helium, there were drifts.
 +      * did not do in-space test due to computation limit on board
 +
 +Noise/band Figure
 +  * Jacques: this one is mostly wrong, no need to discuss. A lot things have been fixed.
 +  * Jacques sends a new figure for Shaul to present. Units are consistent between bands and signals.
 +  * Synchrotron not completely clear
 +  * BB dominated by lensing
 +  * Shaul: six dark blue bands are wrong, should be three
 +  * CO lines
 +  * Current units are for broader community, who do not understand uK.
 +
 +
 +Shaul will be gone for next 3 weeks until June 18th. After Shaul comes back, report writing mode.
 +
 +
 +
  
imagerteleconnotes20180523.1527096219.txt.gz · Last modified: 2018/05/23 12:23 by hanany

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