NICMOS
Cooling System Status
Larry Petro
April 4, 2002
Summary
❖
NICMOS continues to cool
➤
❖
NCC not surging, increasing cooling
➤
❖
NICMOS is safed in order to accelerate cooling
Occurred later than expected
NCS performance improvements under study
April 4, 2002
TIPS
2 / 10
Significant activities
❖
❖
Turboalternator speed increased 100 rps (3/24)
➤
Cause unknown
➤
Improved cooling of NICMOS
NICMOS safed (3/28)
➤
❖
Reduces heating in circulator loop by 0.1-0.2 W
NCC surging stopped (4/3)
➤
➤
April 4, 2002
Turboalternator inlet temperature 85 K (>90 K in
ground tests)
Compressor speed limit (7090 rps) in effect until 80 K
TIPS
3 / 10
Cooldown continues
L. Bergeron
Actual NICMOS Cooldown, Compared to Model Prediction
280
260
240
200
180
NICMOS switched off
Temperature (K)
220
160
8888 Detector
Neon at N2 tank
MNPNCOLT
(NICMOS Outlet Temp)
120
NDWTMP21 (Cold-Mask Temp, VCS front)
100 NDWTMP25 (VCS aft)
NFPA1TMP (Camera 1 FPA Temp)
80
MNPTAILT (TBA Inlet Temp)
140 87007
60
0
April 4, 2002
1
2
3
4
5
6
7
8
9
10
11
12
Time since Compressor startup (Days since 2002 Day 78, 00:23.328 UT)
TIPS
13
14
15
16
4 / 10
NICMOS cooldown
L. Bergeron
NICMOS Inlet Temperature
135
NFPA1TMP
NFPA2TMP
NFPA3TMP
130
125
120
110
105
NICMOS switched off
Temperature (K)
115
100
95
90
MNRNCILT (NICMOS Inlet Temp)
MNPNCOLT (NICMOS Outlet Temp)
MNPLINTT (Comp/Circ Load Interface Temp)
85
80
75
7
April 4, 2002
8
9
10
11
12
13
Time since Compressor startup (Days since 2002 Day 78, 00:23.328 UT)
TIPS
14
15
16
5 / 10
Cooldown rate
C. Long
April 4, 2002
TIPS
6 / 10
NCC surging stopped
•
Compressor
•
Surging
400 rps
No surging
NCC Speeds & Temperature
8000
92
7000
90
6000
88
5000
86
4000
84
3000
82
2000
80
1000
0
0:00:00
Compressor
TBA
TBA inlet temperature
NICMOS inlet temperatur
2:24:00
4:48:00
Inlet Temperature = 85K
Kelvins
Speed Revs/sec
Turboalternator
78
7:12:00
9:36:00
12:00:00
14:24:00
16:48:00
76
19:12:00
Time Day 093 (hr:min:
April 4, 2002
TIPS
7 / 10
Ultimate detector temperature?
T= a(0) * exp( (x+a(1)) * a(2) ) + a(3)
230
220
["NICMOS OFF" range]
fit range
TBA speed increase
210
200
MNPNCOLT (NICMOS Outlet Temp Data)
MNPNCOLT (NICMOS Outlet Temp Fit)
a(0)=139.83409
a(1)=-79.407515
MNPTAILT (TBA Inlet Temp Data)
a(2)=-0.16725383
MNPTAILT (TBA Inlet Temp Fit)
a(3)=96.473789
a(0)=103.60486
a(1)=-77.500066
a(2)=-0.10552370
a(3)=68.224042
190
Temperature (K)
180
170
160
150
140
130
120
No surging
NICMOS safed
110
100
90
80
78
80
82
84
86
88
90
92
94
2002 Daynumber
96
98
100
102
104
100 K in
2 weeks
without
further
improvements
L. Bergeron
April 4, 2002
TIPS
8 / 10
Possible improvements
❖
Lower NCC heat rejection interface
temperature
➤
❖
❖
Lower CPL reservoir minimum temperature from -10 C
to -12 C to -15 C
Increase NCC compressor speed
➤
7300 rps present limit
➤
7400 rps under consideration
Modify circulator loop
➤
April 4, 2002
Increase speed & pressure
TIPS
9 / 10
NCS Status
❖
NCS performing nominally
❖
Cryovalve heater operating nominally
➤
No leakage past o-rings
AS pressure declined from 1.2×10-6 to 0.7×10-6 torr
Occasional 3× spikes (< 2×10-6 torr)
➤
Heater power cycle is nominal (40- 50 %)
60 - 70% occasionally
❖
NICMOS cooling rate is slower than expected
April 4, 2002
TIPS
10 / 10