LYRA Tests and SelectionsLYRA Tests and Selections

SCSL Meeting Bern 29 Nov - 01 Dec 2006

LYRAthe Lyman-alpha Radiometer onboard PROBA-2

I. From Model to Configuration

II. BESSY Campaigns

a. Flux Linearity

b. Stability, Drift

c. LEDs, Dark Current

d. Spectral Responsivity

e. Homogeneity, Flatfield

III. Summary

Contents

I. From Model to ConfigurationI. From Model to Configuration

Choice of filters: Zirconium (150 nm, 300 nm), Aluminium, Lyman-alpha (N, XN, VN, and combinations thereof), Herzberg, …

Choice of detectors: MSMxx (diamond), PINxx (diamond), AXUVxx (silicon), …

- Tested separately to find transmittance and responsivity- Simulated with TIMED-SEE solar spectra to find expected response values and purities

cf. http://lyra.oma.be/radiometric_model/radiometric_model.php

Example: “high” flux + “Herzberg” filter + “PIN” detector

Selected configurations:

filter detector nominal FWHM measured

1-11-1 Ly XN + MSM12 121.5 +/- nm 116-126 nm1-21-2 Herzberg + PIN10 200-220 nm 197-218 nm1-31-3 Aluminium + MSM11 17-80 nm (1)-2.4, 17-35 nm1-41-4 Zr (300nm) + AXUV20D 1-20 nm (1)-1.3, 6-15 nm

2-12-1 Ly XN + MSM21 121.5 +/- nm 116-126 nm2-22-2 Herzberg + PIN11 200-220 nm 199-219 nm2-32-3 Aluminium + MSM15 17-80 nm (1)-1.4, 17-27 nm2-42-4 Zr (150nm) + MSM19 1-20 nm (1)-1.3, 6-12 nm

3-13-1 Ly N+XN + AXUV20A 121.5 +/- nm 116-126 nm3-23-2 Herzberg + PIN12 200-220 nm 198-219 nm3-33-3 Aluminium + AXUV20B 17-80 nm (1)-2.4, 17-35 nm3-43-4 Zr (300nm) + AXUV20C 1-20 nm (1)-1.3, 6-15 nm

Consequence:

- All channels individual- No simple redundancy- Combined responsivities- New estimates for response and purity (cf. II d.)

II. BESSY Campaigns

- NI beamline (40 – 240 nm, 60 C) July 2005 Doc. RP-ROB-LYR-0132-NI-July2005

- GI beamline (1 – 30 nm, 60 C) July 2005 Doc. RP-ROB-LYR-0132-GI-July2005

- (Final) NI beamline (40 – 240 nm, 37 C) March 2006 Doc. RP-ROB-LYR-0132-NI-March2006

- (Final) GI beamline (1 – 30 nm, 37 C) March 2006 Doc. RP-ROB-LYR-0132-GI-March2006

a. Flux Linearity

- Using different aperture stops, or- Varying exit slit of monochromator- Relation fitted (2006) with a function I=[c+]a*P^b- Results: almost linear, slightly sub/superlinear,

sub/superlinear (qualitatively)- or: b~1, c~0 (quantitatively)

Results in detail:

NI 2006 GI 2005 NI 2006 GI 2006 (121.6 nm, 200 nm) (20 nm, 10 nm) (121.6 nm, 210 nm, 50 nm) (18 nm, 10 nm)

1-11-1 MSM slightly sublin. 0.995721-21-2 PIN slightly superlin. 1.006561-31-3 MSM 0.98565 1.1719, but c>01-41-4 AXUV 1.00155

2-1 2-1 MSM slightly sublin. 1.036612-2 2-2 PIN slightly superlin. 0.994832-32-3 MSM superlinear 1.02234 0.978942-42-4 MSM slightly superlin. 1.04009

3-1 3-1 AXUV almost linear 1.024343-23-2 PIN almost linear 0.995293-33-3 AXUV sublinear 0.00230 0.992533-43-4 AXUV almost linear 1.00064

b. Stability, Drift

- Shutter was opened and closed every 60 s, then every 600 s

- Some additional longer tests were executed- BESSY 2005 campaigns (60 C) still to be analyzed in

detail- LED values, dark current values and 44 C, 50 C

temperature effects: see below

Example: Channel 2-1 (Ly XN + MSM21) at BESSY NI 2006

Results (2006) in detail:

start drift stop (“slow” ~min, “almost immediate” ~s) (“tail” ~min, “almost immediate” ~s)

1-11-1 MSM slow upward tail1-21-2 PIN almost immediate (almost) no almost immediate1-31-3 MSM almost immediate, slow upward tail, almost immediate1-41-4 AXUV immediate no immediate

2-12-1 MSM slow upward tail2-22-2 PIN almost immediate (almost) no immediate2-32-3 MSM slow upward almost immediate2-42-4 MSM slow upward almost immediate

3-13-1 AXUV (almost) immediate (almost) no almost immediate3-23-2 PIN almost immediate no immediate3-33-3 AXUV (almost) immediate (almost) no (almost) immediate3-43-4 AXUV immediate no almost immediate

c. LEDs, Dark Current

visLED uvLED offset @37 C 44 C 50 C

1-11-1 MSM (0.005) (0.024) 0.001 0.0101-21-2 PIN 0.004 0.014 0.000 -0.0021-31-3 MSM (0.100) 0.000, -0.007 0.003 0.0101-41-4 AXUV -0.004

2-12-1 MSM (0.012) (0.023) 0.001 0.0092-22-2 PIN 0.015 -0.001 -0.002 -0.0052-32-3 MSM ((0.016-0.136)) 0.000, -0.008 0.002 0.0072-42-4 MSM -0.001

3-13-1 AXUV 0.000? 0.000 0.002 0.0083-23-2 PIN 0.006 -0.003 -0.0053-33-3 AXUV (1.059) -0.001, -0.011 -0.003 -0.0053-43-4 AXUV -0.014

All values in nA(x) = varying around x, ((x-y)) = unstable from y to x, “negative” current values due to conversion

d. Spectral Responsivity

- Filters and detectors measured together (“channels” as configurated)

- Relevant spectral range is tested, with special attention to range borders

- V changed to A using appropriate gain resistor- Corrections for ring current applied

Example: “high” solar flux simulated with measurements of channel 1-1 (Ly XN + MSM12) at BESSY NI 2006

- How to estimate “correction factors”?- Consequences for data levels?

Expected Signal and Purity

theorectical: “min” “high” measured: “min” “high”

1-11-1 MSM 0.139 nA (37%) 0.161 nA (44%) 0.240 nA (24%) 0.267 nA (30%)1-21-2 PIN 12.75 nA (86%) 12.77nA (86%) 12.57 nA (83%) 12.59 nA (83%)1-31-3 MSM 0.120 nA (61%) 5.264 nA ( 3%) 0.086 nA (58%) 4.945 nA ( 3%)1-41-4 AXUV 0.530 nA (99%) 15.37 nA (88%) 0.699 nA (100%) 19.09 nA (100%)

2-12-1 MSM 0.115 nA (39%) 0.135 nA (46%) 0.104 nA (21%) 0.114 nA (26%)2-22-2 PIN 13.80 nA (83%) 13.82 nA (83%) 13.75 nA (84%) 13.76 nA (84%)2-32-3 MSM 0.127 nA (73%) 3.821 nA ( 6%) 0.074 nA (59%) 3.837 nA ( 3%)2-42-4 MSM 0.111 nA (99%) 2.878 nA (100%) 0.094 nA (100%) 2.772 nA (100%)

3-13-1 AXUV 0.132 nA (46%) 0.156 nA (54%) 0.113 nA (81%) 0.148 nA (84%)3-23-2 PIN 10.20 nA (85%) 10.22 nA (85%) 10.15 nA (83%) 10.16 nA (83%)3-33-3 AXUV 1.072 nA (75%) 34.95 nA ( 6%) 1.090 nA (72%) 36.83 nA ( 5%)3-43-4 AXUV 0.530 nA (99%) 15.37 nA (88%) 0.710 nA (100%) 19.31 nA (100%)

Calibration Factor, Data Levels

How to estimate the solar signal from the LYRA signal?

LYRA signal * purity / area / responsivity = solar signal[A] [%] [m2] [A W-1] [W m-2] \___________________/ calibration factor

Example: “max”, “high”, “min” flux + Channels 1-1, 1-2, 1-3, 1-4

- Use constant factor, linear dependency on signal, knowledge about solar flux?

- Change public data each time when calibration factor gets more realistic? Use different data levels?

e. Homogeneity, Flatfield

Example: Channel 2-3 (detector diameter 4.2 mm)

What consequences will an off-pointing have?

III. Summary

Linearity Stability LEDs Signal, Purity

1-11-1 MSM + -- + -1-21-2 PIN + + + ++1-31-3 MSM --- - +? --1-41-4 AXUV + + ?? +++

2-12-1 MSM + - + -2-22-2 PIN + + + ++2-32-3 MSM -- - -? --2-42-4 MSM + - ?? +++

3-13-1 AXUV + + - +3-23-2 PIN + + +? ++3-33-3 AXUV - + +? --3-43-4 AXUV + + ?? +++

Recommendation

Head 2 should be nominal Head 1 should be used once a week Head 3 should be used once a month

depending on the behaviour of LYRA (deterioration etc.)