Pop-up detector tests

Darren Dowell -- (626)395-6610 (office), -2600 (lab), 796-8806 (FAX)

Last modified Friday, 21-Apr-2000 10:00 PDT
cdd@submm.caltech.edu

Thermistor Variety Pack -- Results -- Apr. 2000

In the future...

Thermal Conductance Variety Pack 5347 -- Results -- Apr. 21, 2000

All bolometers are wired with 30 Mohm nichrome load resistors. They were measured with two separate cooldowns between which the routing of the 16 JFETs was changed.

Sample IV curves for a bolometer at multiple temperatures:

In the above graph, the filled circles are measured data, and the lines are model fits with 4 free parameters.

The preliminary summary of bolometer parameters is as follows:

G0 test array 5347 LH1
Data at 330, 440, 597, 742, 985, 4243 mK (pixels 1-16)
Data at 329, 448, 604, 744, 974, 4261 mK (pixels 17-32)
Updated 21 Apr 2000, 09:45 PDT

R = R0 exp(sqrt(T0/T))
G = G0 T^beta

                        R*
          R0    T0    0.3 K   G0=G(1 K)          G(0.3 K)*  G(0.5 K)
bol/grp  ohms    K    Mohms  W/K^(beta+1)  beta     W/K       W/K
-------  ----  -----  -----  ------------  ----  ---------  ---------
01  mem. 1844  26.25   21.3    23.3 e-9    0.55  12.1  e-9  15.9  e-9
02  ??   1290  25.58   13.2     1.07e-9    1.32
03  ??   1365  25.51   13.8     1.20e-9    1.19   0.29 e-9   0.53 e-9
04  ??   1401  25.31   13.7     0.94e-9    1.15
05  3D   1953  26.94   25.5    24.4 e-9    1.97
06  3D   1956  27.16   26.5    24.1 e-9    1.96   2.28 e-9   6.19 e-9
07  3D   2147  27.11   28.9    19.4 e-9    1.77
08  3C   2127  26.93   27.7     2.24e-9    1.20
09  3C   1844  27.58   26.9     2.66e-9    1.38   0.51 e-9   1.02 e-9
10  3C   1898  27.05   25.2     2.61e-9    1.35
11  3B   1934  28.40   32.5    24.2 e-9    2.03
12  3B   1908  28.51   32.7    25.1 e-9    2.06   2.10 e-9   6.02 e-9
13  3B   1869  28.76   33.4    27.8 e-9    2.14
14  3A   1840  28.67   32.4     4.08e-9    1.44
15  3A   1951  28.41   32.9     3.80e-9    1.42   0.69 e-9   1.42 e-9
16  3A   1924  28.37   32.2     3.89e-9    1.41
17  2D   1893  28.73   33.7    38.4 e-9    2.63
18  2D   1899  28.90   34.8    38.7 e-9    2.66   1.57 e-9   6.12 e-9
19  2D   1981  28.82   35.8    36.7 e-9    2.65
20  2C   2025  28.51   34.7     1.17e-9    1.35
21  2C   1839  28.97   34.1     1.31e-9    1.43   0.23 e-9   0.49 e-9
22  2C   1920  28.91   35.2     1.26e-9    1.40
23  2B   1957  29.47   39.4     1.21e-9    1.37
24  2B   2038  29.15   38.9     1.17e-9    1.34   0.23 e-9   0.46 e-9
25  2B   1929  29.84   41.4     1.25e-9    1.40
26  2A   1871  30.40   44.0    42.4 e-9    2.76
27  2A   2019  29.93   44.0    37.3 e-9    2.62   1.59 e-9   6.07 e-9
28  2A   1952  30.41   46.0    40.0 e-9    2.69
29  1A   1836  31.16   49.0    20.0 e-9    2.74
30  1A   1788  31.95   54.2    20.7 e-9    2.80   0.71 e-9   2.97 e-9
31  1A   1927  31.34   52.9    18.1 e-9    2.68
32  mem. 1814  32.12   56.5    72.9 e-9    1.58  10.9  e-9  24.4  e-9

* extrapolation

Resistance Gradient

The 0.327 K resistance goes from high at bolometer 32 to low at bolometer 1, as measured in the linear portion of the IV curve with an electrometer:

           Resistance
Bolometer     Mohm
---------  ----------
    1         15.6
    9         19
   12         23
   15         22
   24         28
   32         36.4

Time Constants, Bolometer 24 (SHARCII candidate)

For the measured quantities, we looked at the transition caused by a positive change in the bias. In almost all cases, the bolometer voltage overshot the final voltage and then settled down to the final value (presumably caused by Z[high frequency] > Z[DC]). Measured quantities:

delta(V) is the voltage from the initial (flat) voltage to the final (flat) voltage.
V(overshoot) is the voltage from the final (flat) voltage to the peak voltage.
t(overshoot) is the time from the beginning of the transition to the peak voltage.
t(settle) is the time from the peak to when the voltage has slewed 63% of the way to the final voltage.

The bolometer voltage has been amplified by a gain of 100 before display on the oscilloscope.

Bias: 15.7 to 23.5 mV square wave at 8 Hz

predicted G: 0.28 nW/K, predicted T: 0.34 K
predicted delta(V): 2.6 mV, observed delta(V): 2.7 mV (RTI)
observed V(overshoot): 0.39 mV
t(overshoot) = 2.4 msec, t(settle) = 4.5 msec

Bias: 35.3 to 43.1 mV square wave at 8 Hz (OPTIMAL BIAS)

Predicted G: 0.31 nW/K, predicted T: 0.37 K
Predicted delta(V): 1.2 mV, observed delta(V): 1.1 mV
observed V(overshoot): 1.1 mV
t(overshoot) = 1.3 msec, t(settle) = 3.6 msec

Bias: 74.5 to 82.4 mV square wave at 8 Hz

Predicted G: 0.38 nW/K, predicted T: 0.43 K
Predicted delta(V): 0.17 mV, observed delta(V): 0.11 mV
observed V(overshoot): 1.2 mV
t(overshoot) = 0.6 msec, t(settle) = 2.3 msec

Bias: 152.9 to 160.8 mV square wave at 8 Hz

Predicted G: 0.50 nW/K, predicted T: 0.53 K
Predicted delta(V): -0.03 mV, observed delta(V): -0.13 mV
observed V(overshoot): 0.74 mV
t(overshoot) = 0.4 msec, t(settle) = 1.3 msec

Time Constants, Bolometer 18 (HAWC candidate)

Bias: 45.1 to 52.9 mV square wave at 40 Hz

Predicted G: 2.1 nW/K, predicted T: 0.34 K
Predicted delta(V): 2.7 mV, observed delta(V): 2.6 mV
t(rise) = 0.38 msec

Bias: 94.1 to 102.0 mV square wave at 40 Hz (OPTIMUM BIAS)

Predicted G: 2.5 nW/K, predicted T: 0.36 K
Predicted delta(V): 1.5 mV, observed delta(V): 1.5 mV
observed V(overshoot): 0.20 mV
t(overshoot) = 0.8 msec, t(settle) = 0.68 msec

Bias: 192.2 to 200.0 mV square wave at 40 Hz

Predicted G: 3.6 nW/K, predicted T: 0.41 K
Predicted delta(V): 0.45 mV, observed delta(V): 0.53 mV
observed V(overshoot): 0.46 mV
t(overshoot) = 0.31 msec, t(settle) = 0.36 msec

Bias: 388.2 to 396.0 mV square wave at 40 Hz

Predicted G: 5.6 nW/K, predicted T: 0.48 K
Predicted delta(V): 0.12 mV, observed delta(V): 0.22 mV
observed V(overshoot): 0.34 mV
t(overshoot) = 0.22 msec, t(settle) = 0.16 msec

Thermal Conductance Variety Pack 5327 -- Results -- Apr. 12, 2000

Tests of G0 array LH5 with 5327 (ND=0.7) doping are complete. Bolometers 17-29 and 32 were wired in series with 150 Mohm SiCr load resistors. Bolometer 30 was shorted with no load resistor, and bolometer 31 was shorted with a load resistor in the circuit. In all cases, the signals were routed to JFET gates. Bolometers 1-16 were not wired. The array was clipped to the detector board with beryllium-copper clips and gold wedge bonded.

Other changes to the system include using only 3 of 4 G10 support tubes, only 2 of 4 manganin cables, avoidance of the surface mount connectors on the detector board, and using gold leaf between the INVAR base plate, detector board, heat strap, and GRT interfaces.

Sample IV curves for all bolometers at a single temperature:

IV curves for a bolometer at multiple temperatures:

In the above graph, the filled circles are measured data, and the lines are model fits with 4 free parameters.

The preliminary summary of bolometer parameters is as follows:

G0 test array 5327 LH5
Data at 328, 342, 389, 467, 651, 860, 962, 4127 mK
Updated 16 Apr 2000, 16:10 PDT

R = R0 exp(sqrt(T0/T))
G = G0 T^beta

            R0    T0     G0=G(1 K)          G(0.3 K)*  G(0.5 K)
bol./grp.  ohms    K    W/K^(beta+1)  beta     W/K       W/K
---------  ----  -----  ------------  ----  ---------  ---------
17  2D     1175  51.70    65.6 e-9    2.92
18  2D     1193  51.94    65.5 e-9    2.91   1.97 e-9   8.71 e-9
19  2D     1242  50.99    63.5 e-9    2.79
20  2C     1400  49.64     1.61e-9    1.24
21  2C     1271  51.22     1.70e-9    1.36   0.33 e-9   0.66 e-9
22  2C     1275  51.06     1.72e-9    1.35
23  2B     1354  50.20     1.65e-9    1.29
24  2B     1403  49.92     1.62e-9    1.28   0.35 e-9   0.67 e-9
25  2B     1304  50.94     1.67e-9    1.35
26  2A     1228  52.05    63.8 e-9    2.88
27  2A     1291  51.77    62.0 e-9    2.83   2.05 e-9   8.72 e-9
28  2A     1268  51.47    63.7 e-9    2.80
29  1A     1232  52.47    25.4 e-9    2.69   1.00 e-9   3.93 e-9
32  mem.   1243  52.25   128   e-9    2.40   7.12 e-9  24.3  e-9

* extrapolation; may not be accurate

Here is a Postscript summary of the bolometer recipes to associate with the group specification in the above table.

Photos:

Implant Test Results -- Apr. 9, 2000

SHARCII Dewar, large ceramic board

graph of R vs. T

A fit to the data with good thermometry yields:

Label   ND   R0 (ohms)  T0 (K)
-----  ----  ---------  ------
5250a  0.6     2570      81.8
5250b  0.6     3880      74.6
5327   0.7     1750      48.9
5347   0.75    2090      25.7

Additional plots:
Christine's plot 4/07/00
Mino's ND=0.7 PDF plot
Mino's ND=0.75 PDF plot

Photos:

SHARCII Dewar, small ceramic package on coldhead

Photo:

Purple Dewar, small ceramic package

Three-element dies were tested using the Goddard-provided ceramic packages attached 'upside down' to a copper block in order to shield the devices from radiation. Resistances were measured with the Keithley 616 electrometer.

purple Dewar implant tests graph of R vs. T

A fit to the data from the purple Dewar experiment only yields:

Label   ND   R0 (ohms)  T0 (K)
-----  ----  ---------  ------
5306   0.65    1670      67.3
5327   0.7     2100      42.7
5347   0.75    2380      23.2

Plans for array package -- Feb. 13, 2000

Photos of the assembled package, minus detector array:

Plans for testing the bolometers -- Feb. 12, 2000

The bolometers will be tested at Caltech in the SHARC II cryostat, which contains a large (14" ID by 20") liquid helium work area with a 3He refrigerator. The minimum operating temperature is 0.285 K.

Test goals

For the bolometers in the test arrays, we want to measure:

G(T) -- thermal properties
R0, T0 -- thermistor properties
Noise spectrum from 1-300 Hz with no radiation load
Low frequency 1/f noise (resistance fluctuations)
Time constants (heat capacity)

The last three items are time consuming to measure, so a subset of bolometers will be measured.

Test procedures

IV curves for all detectors
1. low frequency square wave bias (+V0, 0); DAS in averaging mode
2. high frequency square wave bias (+V0, -V0); DAS in demodulation mode
3. electrometer method confirmation of some bolometers
Noise spectrum, DC bias
1. DAS in demodulation mode; multiple frequencies
2. spectrum analyzer confirmation/calibration of some devices
Low frequency noise spectrum, square wave bias (+V0, -V0); DAS in demodulation mode
Electrical time constants -- Infrared radiation response and bias change response have the same time constant (Mather, 1982).
1. sharp square wave bias (+V0, +V0+delta); DAS recording single frames at 1 kHz
2. sharp square wave bias (+V0, +V0+delta); observe transition on oscilloscope
3. sine wave bias (+V0, +V0+delta); observe phase shift on oscilloscope

For all measurements except the electrometer IV curves, JFETs are required. Items in red are measured one device at a time.

Since we will only have JFET modules to service 16 bolometers, two cooldowns will be required to test a single array. Given two arrays, we will need 4 cooldowns, with tests lasting approximately 1 month.

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