Instrumentation data for low energy solar cosmic ray measurements using OGO-F satellit

Burtis, D. W.

Masley, A. J.

Satterblom, P. R.

Wolpert, M. H.

English

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DOUGLAS PpPm 4906 
FEBRUAR; 1968 
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ff 653 July65 . 
A LOW-ENERGY SOLAR COSMIC RAY EXPERIMENT FOR OGO-F 
M.H. WOLPERT 
D.W. BtlRJlS 
* and 
A.J. MASLEY 
P.R. SATTER~LOM 
Presented at the 14th Nuclear Science Symposium 
Los Angeles, California 
31 October - 2 November 1967 
DOUGLAS MISSILE & SPACE SYSTEMS DIVISION 
MCDONNELL DOUGLAS ,;Lp-- 
CORPORATlON 
https://ntrs.nasa.gov/search.jsp?R=19680023689 2020-03-12T06:32:36+00:00Z
A LOW-ENERGY SOLAR COSMIC RAY EXPERIMENT FOR OGO-F 
by 
M. H. Wolpert, P. R. Satterblom 
D. W. Burtis and A. J. Masley 
Space Physics Brazch 
Space Sciences Department 
Missile & Space Systems Division 
t. 
I 
I I) 
I ABSTRACT 
b The Douglas OGO-F Low- Energy Solar Cosmic Ray Experiment measures  
the differential energy spectrum of protons (5 MeV to 80 MeV) and alphas 
(18 MeV to  160 MeV) using two double-diffused, totally depleted silicon ~ 
I diodes. The pulse amplitude discrimination system, the data multiplexing 
I scheme, and the in-flight calibrator a r e  discussed. 
I ACKNOWLEDGEMENT 
This paper is based on work performed under NASA Contract No. NAS 5-9324. 
i 
INTRODUCTION 
This experiment was originated and designed by the Douglas Space Sciences 
Department to study solar  cosmic radiation. The objectives of this study a r e  
to  help understand solar  cosmic ray acceleration mechanisms, interplanetary 
propagation, and interactions with the Earth 's  magnetic field and ionosphere. 
Protons and alpha particles a r e  identified and their  intensity and energy dis- 
tribution determined. 
OGO-F satellite, i s  capable of measuring events more  intense than any pre-  
viously observed. 
The experiment, which will be orbited on the polar 
SENSORS 
The instrument uses  two double-diffused, totally depleted silicon diodes a s  
detectors. 
TELESCOPE 
A schematic of the detector telescope configuration is shown in Figure 1. 
The detectors a r e  located on a common axis with a separation of 36 mm. 
The cone half-angle i s  28". The entrance to  the telescope i s  covered with a 
2 38. 5 m g / c m  
3. 4 MeV. 
front detector and to  reduce the effect of electron funneling. 
factor  of the front detector and collimator i s  GA = 2. 674 cm -s ter .  
2 telescope has G 
(= 43p) nickel foil that stops protons with energies less  than 
The collimator is  designed to limit the geometry factor of the 
The geometry 
2 The 
= 0. 545 c m  -s ter .  T 
SYSTEM BLOCK DIAGRAM 
Figure 2 depicts a system block diagram separated into five logic sections. 
. .  Sectioii I ,  the Particle Sorter, aiiip:itide, S G ~ ~ S  cGine;deEt F G I S ~  pairs i ~ t ~  
alphas and protons. The second section, the Pulse-Height Analyzer (PHA), is 
employed to divide the amplitude ranges into 11 alpha and 12 proton channels. 
1 
M-36005 B 
DOUGLAS OGO-F SOLID STATE DETECTOR TELESCOPE 
A 
222 mm 
R = 0.84cm 
2 -
Ioop B 
366 mm 
R = 1.0&m 
2 
-
F P  
2 Gte, = 0.545cm -ster 
2 GA = 2.67cm - ster 
* FIGURE 1 
M-451338 SYSTEM BLOCK DIAGRAM 
1 ------ LINEAR CLOCK 
GATE CONTROL 
1 
LINEAR 2 MHz 
GATE CLOCK 
I 
PULSE I B @+I 
GEN lEz?.z+p DISC 
E ml PULSE GEN I DISC I - . 
I IN-FLIGHT CALIBRATOR  ARTICLE SORTER ' ' PULSE HEIGHT ANALYZER 
I------- ------ --&--- ---- 
SHIFTING ACCUMULATOR 
NO. 10 
I 
TELEMETRY I LACCUMULATOR - ------------ -- 
I 
I 
FIGURE 2 
2 
The third section, Accumulation and Multiplex, is used to  funnel the 30 
channels of experiment information into ten shifting accumulators. 
Commutator Control is the fourth section. 
I The Main 
Its function is to interface space- I 
I 
~ craft  system timing with output information. Section 5, the In-Flight 
I 
I Calibrator (IFC) measures  the gain of each amplifier, the threshold of each 
I discriminator and PHA channel, and tests overall system operation. 
EXPERIMENT INFORMATION 
The 30 channels of experiment data a re  shown in Figure 3. Channels 1 I 
I 
I 
through 14 a r e  proton data, and Channels 15 through 26 a r e  alpha data. 
remaining four channels a r e  I1 through I3 and a source-IFC channel. 
through P14 and A2 through A12 a r e  outputs of the Pulse-Height Analyzer. 
The 
I 
P 3  
I 
I 
I ?  
I 
P1 and P 2  and A1 a r e  obtained f rom window discriminators and rrandrr gates 
i n  the Part ic le  Sorter. 
CHANNEL 
(NO.) 
1 
2 
13 
14 
M-28796 A 
TABLE OF DIGITAL ACCUMULATOR 
OUTPUT CHANNELS 
ENERGY (MeV) CHANNEL ENERGY (MeV) 
PROTONS (NO.) 
ALPHAS 5 -  6 P1 
6 -  8 P2 21 5 6 -  67 A7 
11 - 13 P4 23 8 0 -  94 A9 
13 - 16 P5 24 94 -112 A10 
16 - 21 P6 25 112 -136 A1 1 
21 - 24 P7 26 136 - 160 A12 
24 - 28 P8 
28 - 33 P9 INTEGRAL CHANNELS 
33 - 39 P10 
39 - 46 P11 
46 - 55 P12 
55 - 6 6  P13 
66 - 80 P14 
ALPHAS ANALOG OUTPUT 
8 - 11 P3 22 67 - 80 A8 
27 P 5 - 8 0  4:21-160 MeV 11  
28 a :  21-160 MeV 12 
29 P >80 MeV 13 
30 SOURCE AND IFC S 
15 18 - 21 A1 1 P 1 5  Meka.21 Mekes0.25KeV 
16 21 - 23.5 A2 
17 23.5 - 28 r.., 
18 28 - 3 6  A4 
19 36 - 4 8  A5 
20 48 - 5 6  A6 
A 2  
FIGURE 3 
3 
PARTICLE SORTING 
The Particle Sorter is shown in detail in Figure 4. 
Model 11 3 flat pack, integrated circuit-amplifier systems a r e  used. 
wave shaping i s  employed, yielding pulses with 400-nsec rise and 1. 5-ysec 
fall times. The frequency response is flat to 50 kHz and falls off by 2 db at 
100 kHz. 
Solid-state Radiations 
RC 
A coincidence circuit, with a resolving t ime of 350 nsec, is employed to 
establish single particle analysis. 
circuit-differential comparitators and a one shot. 
cidence circuit is fed to a delay generator so that the coincidence pulse may 
also be used a s  a strobe for  the t tand't  gates. 
The circuit consists of two integrated 
The output of the coin- 
Pulses from the A and B amplifiers a r e  fed to seven differential amplitude 
discriminators. Complementary outputs f rom each of the discriminators 
4 
FIGURE 4 
a r e  available for full logic flexibility. 
produces uniform output pulses. 
RC feedback around the discriminator 
Par t ic le  sorting and signature is obtained f rom six rlandtl gates. The I1andtl 
gates, labelled alpha, enable o r  proton enable when satisfied, select either 
A o r  B amplifier signals, respectively, for pulse-height analysis. The alpha 
Ilandl' gate is also the second integral channel. 
P1, P3, I1 and 13. 
f rom protons with energy greater  than 80 MeV. 
The other four gates select 
A log-rate meter is used to  count a l l  B amplifier pulses 
The logic of this section has  been operated at 100 kHz with no loss of 
information. 
PULSE-HEIGHT ANALYZER 
The Pulse-Height Analyzer is shown in Figure 5. 
run-down-type analyzer that sor t s  alphas f rom 26 to 140 MeV into 11 channels 
It is a 16 channel, RC 
M-451328 
PULSE HEIGHT ANALYZER 
ACCUMULATOR 
ENABLE e- a ENABLEOS LINEAR - 
DR I VER 
I '  
p w  LINEAR 
GATE P ENABLECH 
MULTIPLEXER M 
FIGURE 5 
I 
5 
and protons f rom 8 to 80 MeV into 12 channels. 
through either the alpha o r  proton linear gate. 
loop peak and hold differential amplifier. 
put voltage r i s e s  toward the input amplitude. 
tudes is compared by a differential stage such that the output, upon exceeding 
the input by a few microvolts, closes the gate. 
toward ground with a t ime constant set  by R 1 
linear rundown is employed to shrink the higher energy and expand the low- 
energy channels, giving r i s e  to  more  evenly spaced energy boundaries. 
Entrance is obtained 
This linear gate is a closed 
When the gate is enabled, its out- 
The difference in these ampli- 
The output voltage then falls 
and C1. This type of non- 
Linearity and amplitude reproduction of the gate has been found to be better 
than 1%. Gate operation up to 50 kHz is easily obtained. 
pedestal is less  than 40mV and extremely stable over temperature. 
ratio of input to output voltages, when the device is off, is better than $ 
1OOO:l. 
The output gate 
The 
The clock control module is an amplitude to t ime converter. 
linear gate output is above the control module's threshold, the 2-MHz clock 
runs. 
is finally decoded and a pulse stored in the appropriate accumulator. After 
the clock starts,  the l inear gates a r e  inhibited for  20 psec, 10 psec to allow 
the flip-flops (F/F) to count and settle, and 10 psec to allow decoding, 
storage, and reset. Sixteen channels a r e  available f rom the analyzer, but 
f o r  this application the eight highest clock-count channels a r e  combined by 
pairing those adjacent, giving 12 separate  channels. 
When the 
Clock counts a r e  then fed to a four bit counter, The binary number 
ACCUMULATOR AND MULTIPLEX 
The Accumulator and Multiplex scheme is shown in Figure 6. 
ment uses 10 shifting accumulators, each of which is  preceded by three  
parallel  gates that alternately select, f o r  fixed t ime intervals, one of the 
three  inputs f o r  accumulation. 
The experi- 
~ ~~ 
ACCUMULATORS AND MULTIPLEXER M-45131 
1 2 3  Q 
ACCUMULATOR ACCUMULATOR 
SPACECRAFT 
TELEMETRY 
FIGURE 6 
During tes ts ,  the accumulators and gates have properly accepted information 
at 150 kHz and the accumulators have accurately shifted out information at 
64 kHZ, the highest telemetry rate. Power requirement for each flip-flop 
under dynamic conditions i s  no greater than 1 .  15 mW. 
MAIN COMMUTATOR CONTROL 
The Main Commutator Control section, Figure 7, controls the accumulation 
periods, the input gate programming, and the shifting of information into the 
spacecraft  telemetry system. Five digital words a r e  assigned to  this exper- 
iment on each telemetry main commutator, or main frame, cycle. The two 
groups of five accumulators each shift out their  contents on alternate cycles. 
While one group of five accumulators is shifting data to the telemetry, it is 
inhibited f r o m  receiving information. 
five accumulators is not inhibited. 
At the same time, the other group of 
Since there  a r e  five assigned words per 
7 
M a 1 3 4  A MAIN COMMUTATOR CONTROL 
ACCUMULATOR 
ACCUMULATOR 
ACCUMULATOR 
ACCUMULATOR 
WORD 1 4EI-b 1 AND 6 
WORD 2 dEw AND 
WORD 3 4EI-b 3 AND 8 
WORD 4 dEw AND 
2 
f 
ACCUMULATOR 
WORD 5 5 AND 10 
54-+ 6 
FIGURE 7 
I 
main frame and 30 experiment channels of information, it requires  six main 
f r ames  to read out a complete experiment cycle. 
plexing method is obtained f rom the two se ts  of th ree  flip-flops, driven by 
Word Buffer 5. 
Timing for the multi- 
Each se t  of flip-flops, which is one main f r ame  out of 
synchronization, has a cycle of six telemetry main f rames  and generates 
three accumulator control signals. 
operate the f i r s t  five accumulators and Control Signals 4 through 6 operate 
the second five accumulators. 
Accumulator control Signals 1 through 3 
Each control signal is  t ton t l  f o r  two main 
f r ames  and t lofft l  for four, allowing the fract ion of accumulation time to be 
3 370. 
IN- FLIGHT CALIBRATOR 
The In-Flight Calibrator (IFC), Figure 8, provides an electronic means f o r  
measuring the reference voltages on each of the seven discriminators,  as 
well as  the channel boundaries of the Pulse-Height Analyzer. Once every 
IN-FLIGHT CALIBRATOR Y-451358 
COUNTER CLOCK 
RAMP 
A 
& +  GEN 
I 
1 ) A M P L I  FlER 
A 
- 
RAMP 1 AMPLIFIER 
23 3 a = )  GEN B 
B 
FIGURE 8 
~4 
160 minutes, a calibration sequence i s  started. The first sequence begins 
20 minutes a f te r  each "power-on" command. During this sequence, seven 
separate  pulse t ra ins  ( ramps) ,  whose pulse amplitudes a r e  linearly 
increasing with time, a r e  generated and routed to the input of the charge- 
sensitive preamplifiers.  
each discr iminator  encompasses i ts  threshold. 
exceed the threshold of that discriminator, which i s  a measure  of the 
discr iminator-reference voltage, i s  counted by one of the accumulators. 
The r a m p  consists of fas t  rise (100 nsec) slow RC decay (10 psec)  pulses at 
.a frequency of 4 o r  6 kHz, depending on the particular discriminator. 
duration of the r amp  i s  216 msec,  which gives approximately 900 o r  
1300 pulses a t  4 o r  6 kHz, respectively. 
i s  bet ter  than 1%. 
The range of amplitudes from the amplifiers into 
The number of pulses that 
The 
The integral linearity of the r amp  
9 
After discriminator calibration, the ramp is routed successively to  each 
input of the PHA. 
pulses that l ie within the boundaries of each channel. 
1 2  separate PHA outputs with ten accumulators, the input gate sequence is  
different for the two proton and alpha PHA input ramps. The calibration 
program takes 43 main f rames ;  however, only during six main frames i s  
there  any loss of normal experiment data. 
i s  within 0. 57% over the operating temperature range. 
All ten accumulators a r e  used to  count the number of 
In order  to cover the 
The accuracy of this calibrator 
In addition to this electronic device, an alpha particle source, Am241, is 
placed between the two detectors on the wall of the spacer separating them. 
The source i s  coated to degrade and broaden the alpha-particle energy 
spectrum. 
threshold will allow an absolute determination of the gains of the amplifier 
systems. 
The measurement of the number of counts exceeding the 2. 7 MeV 
The output pulse rate of the 2. 7-MeV discriminator is  monitored, 
by the Source-IFC channel, once every six main frames.  During alternate 0 
accumulations of the IFC channel, the amplifier pulses a r e  sent to the 
discriminator. 
B pulses greater  than 2. 7 MeV. 
every 24 main f r ames  the output of this channel i s  programmed to be nine 
binary "ones", which serve a s  a flag for  data processing synchronization. 
The output records:  B pulses grea te r  than 2. 7 MeV; A and 
The cycle is  then started again. Once 
EXPERIMENT PARAMETERS 
The package i s  located within the main body of the satellite, facing away 
f r o m  the Earth. 
c ra f t  power, and is 20 x 20 x 10 cm. 
The experiment weighs 6 lb, requires  2. 2 W a t t s  of space- 
The expected launch date is  late 1968. 
DOUGLAS MISSILE 6 SPACE SYSTEMS DIVISlON 
5301 Bolsa Avenue Huntington Beach. California 92646 
MCDONNELL 


A low-energy solar cosmic ray experiment for OGO-F

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