Variable-delay Polarization Modulators (VPMs)

D. Chuss, G. Novak

7/27/07

Variable-delay Polarization Modulator(VPM)

Advantages of VPMs

• Can be made intrinsically broadband• Can measure circular polarization- a

potentially useful systematic check of instrument

• Used in reflection- no dielectrics to introduce differential loss.

• Employs small, linear motions rather than large circular ones- A reliability issue.

Hertz/SMTONASA/GSFC: D. Benford, D. Chuss, M. Jackson, H. Moseley, J. Staguhn, G.

Voellmer, E. Wollack

Northwestern University: G. Novak, M. Krejny (GSRP)

University of Arizona: C. Walker, C. D. d’Aubigny, C. Kulesa, D. Golish

University of Chicago- R.F. Loewenstein

Using a pair of VPMs, we have integrated the 350 micron, 32 pixel polarimeter Hertz onto the SMTO in Arizona.

QVI 1: Selects Between Q & U(Grid wires at 22.5 degrees)

QVI 2: TogglesRoles of detectors(Q->-Q)(Grid wires at 45 degrees)

Dual Modulators

Hertz/VPM

Instrumental polarization- preliminary result

Q=0.8 +/- 0.3%

U=0.01 +/- 0.02%

Data taken 4/24/07

Jupiter

29 observations

tau~0.07, el=33 deg.

NU Lab Tests- July 2007

HAWC/VPM Integration

VPM “Walkoff” Systematic

• When placed at or near an image plane, the image formed by each polarization will be shifted relative to one another.

Geometry

Density Matrices

Unpolarized Radiation Field

Walkoff

Polarization Modulation

Unpolarized Airy Disk, 53 microns

Analyzer misalignment: 1 degrees

Image Translation (53 microns)

Grid-Mirror Separation Image Shift (arcsec)

14.1 microns 0.04

28.2 microns 0.08

42.3 microns 0.12

Kilo-pixel Backshort-Under-Grid TES Arrays

D. Chuss

7/27/07

Basic TES Circuit

Benford et al. IJIRMMW

Allen et al. (2006)

Irwin et al. (2004)

Time-Domain Multiplexing

GSFC BUG Architecture

Allen et al. (2006) Staguhn et al. (2006)

Pixel Frames

Allen et al. (2006)

Indium Bump-Bonding

Large Format Arrays

• 32 x 40 pixel arrays proposed as a continuation (ROSES)

• These will be mated to the SCUBA MUXes

• Pending funding, expected readiness date: late 2009

• Warm Electronics- suggest UBC source