The Cosmic Ray Nuclei (CRN) detector was designed to measure elemental composition and energy spectra of cosmic radiation nuclei ranging from lithium to iron. CRN was flown as part of Spacelab 2 in 1985, and consisted of three basic components: a gas Cerenkov counter, a transition radiation detector, and plastic scintillators. The results of the experiment indicate that the relative abundance of elements in this range, traveling at near relativistic velocities, is similar to those reported at lower energy

Lheureux, Jacques

Meyer, Peter

Muller, Dietrich

Swordy, Simon

English

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NUCLEI (CRN)
Report
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N91-22063
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0007617
COSMIC RAY NUCLEI (CRN)
DETECTOR
INVESTIGATION
FINAL REPORT
JANUARY 3, 1991
CONTRACT NAS8-32828
SUBMITTED TO:
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
GEORGE C. MARSHALL SPACE FLIGHT CENTER
PREPARED BY:
THE UNIVERSITY OF CHICAGO
933 EAST 56th STREET
CHICAGO, ILLINOIS
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1. Report No
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EDSMIC RAY NUCLEI DETECIDR Ih_TESTIGATION
7. Amh=(,) Peter Meyer
Dietrich M_ller
Jacques L'Heureux
Simon Swordy
9. PerlofmmgOrgeniJmtionNlme endAdckm
The University of Chicago
933 East 56th Street
Chicago, Illinois 60637
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National Aeronautics and Space Administration
Washington, D.C. 20546-0001
George C. Marshall Space Flight Center
Marshall Space Fliqht Center r AL 35812
15. Suppiem_lany Not_
3. Recq)_ent'l Cmat_ NO.
5. Report Orate
January 3, 1991
15. Perloqm_ Orgsrl_ltJ041
e. Porlo, r.ing (_'Om_otk)n Flepo. No.
10. Work Unit No.
11. Contr_l m Gr_m! No.
NAS8-32828
13. Type of Report and Period COVenKJ
Final Report
14. S_ AI_.¢Y Code
16..,t q 4;_r.¢1
The Cosmic Ray Nuclei (CRN) detector was designed to measure elemental
composition and energy spectra of cosmic radiation nuclei ranging from
Lithium to Iron. CRN was flown as part of Spacelab-2 on the Space
Shuttle Challenger in 1985. CRN consisted of three basic components:
(i) a gas Cerenkov counter, (2) a transition radiation detector, and
(3) plastic scintillators. The results of the experiment indicate that
the relative abundance of elements in this range traveling at near
relativistic velocities is similar to those reported at lower energy.
17. Key Wrack ISugg_mcl by Au_rlell
Cosmic Rays
Cosmic Radiation
Spacelab-2
Transistion Radiation
19. Serurtly Ctlamt. Io4 thl= repro1)
Unclassified
NASA FORM 1626 OCT 116
18. [kadt_butkx"lStatement
Unclassified - Unlimited
j onc ass    _ 21. No. of _ ]22.
FINAL REPORT
NASA CONTRACT NAS 8-32828
Peter Meyer, Dietrich Mfiller, Jacques L'Heureux, Simon Swordy
University of Chicago, Enrico Fermi Institute
Chicago, Illinois
January 3, 1991
1. Introduction and Summary
Under the above contract the University of Chicago designed, built and delivered the
CRN instrument for flight in the Spacelab-2 configuration. The instrument was flown
from July 29 to August 5, 1985 on the Space Shuttle Challenger. The performance of our
experiment was entirely successful and we reached our scientific goals. Multiple demands
on the spacecraft limited the observation time. The contract provided for transport of the
instrument back to Chicago, for postflight testing, and for preparation to storage. The
first year of data analysis was covered under the contract as well. Subsequent analysis was
funded under grant NAG W-1311 by NASA Headquarters.
In the following we shall give a condensed account of the activities under the above
contract. The majority of the scientific results obtained with the instrument have been
presented at international conferences and published in several papers. In addition, details
on the design, technical properties of th_ apparatus and performance were published in
the literature. We attach copies of these papers and consider them a major part of this
report.
2. The Staff
The Original proposal for this experiment was submitted in 1976 in response to AO-
OSS-2-76 by P. Meyer and D. Mfiller as Co-PI and James Lamport as Co-I. Shortly alter
selection for flight in 1977 the scientific team was enlarged by Jacques L'Heureux and
Simon Swordy as Co-I. Lamport, after his retirement, resigned from his role as Co-I.
L'Heureux (Senior Research Associate), aside from his individual contributions, took
on the role of Managing Project Scientist. Don Bonasera (Senior Electronics Engineer)
was Project Engineer and head of the electronics group (E. Drag, W. Harvey, W. Hollis);
W. Johnson (Senior Mechanical Engineer) carried the responsibility for mechanical design
and fabrication; Roger Ray (Supervisor, Systems Analyst) headed the software and pro-
gramming group (J. Berger, L. Glennie) that produced software for the onboard processor
and the ground support equipment for preflight tests and flight.
3. Design and Fabrication
The above group, under the guidance of the investigators, carried out the design and
fabrication of the instrument. Most of the components (mechanical and electrical) were
produced at the University's Central Shop and by the electronics group with the help of
capablegraduate and undergraduatestudents. Specialcomponents(instrument container,
valves,etc.) were procured from vendors.
Two important technical advancesshould be reported here. The six large multiwire
proportional chambersthat are part of the transition radiation detectors have thin 2m x
2m mylar windows. Gas must continually stream through them. To avoid any bulging
of the windows the pressure differencebetween chambersand instrument shell had to
be kept below 10-_ atm. A special sensitive pressurecontrol gauge was developedJn
the laboratory that fulfilled this requirement and worked perfectly through the flight (see
attached instrument publication).
The secondimportant advancewas the recognition that the radiator for the transi-
tion radiation need not be made of large numbersof polyethylene foils as was originally
proposed,but could, without lossof efficiency,be composedof thin fibers. Such fibers of
polyolephin areusedcommercially for thermal insulation, are inexpensive,and can readily
be packed into layers. With acceleratorruns (synchrotron of the University of Bonn and
Fermi National Accelerator Laboratory) we could verify that fibers can replace foils as
radiators with no lossin performance.
4. Accelerator Calibrations
(a) The Multiwire Proportional Chambers(MWPC)
The CRN instrument is capableof observing individual cosmic ray nuclei of the el-
ements from Boron (Z=5) to Nickel (Z=28). To cover this wide dynamic range requires
optimization of the multiwire chamberparameters. In particular one has to choosethe
gasmixture and the best operating high voltage. Beamsof energeticheavy particles from
the Berkeley Bevalac were used to carry out this optimization, using several prototype
chambers.
(b) The Transition Radiation Detector (TRD)
The useof TRD's for measuringthe energyof heavynuclei is anentirely new technique,
usedfor the first time in this experiment. Sincethere exist no accelerators that produce
heavy nuclei of sufficient energy,the calibration of the TRD had to be done with singly
chargedparticles, madeavailableto usat FNAL (Fermilab) and at the electron synchrotron
of the University of Bonn, Germany. A prototype TRD with the samenumber of radiators
and MWPC's as the flight unit was constructed and exposed to beams of protons, r-
mesons, p-mesons, and electrons. In this manner, a complete calibration could be obtained.
In-flight check of the calibration was possible over a limited range of energies using Fe
nuclei.
5. Environmental Tests
(a) Mechanical: pressure, vibration, acoustic, temperature
The instrument container and gas containers were designed to meet safety regulations
for manned flight. The instrument container that must withstand 1 atm. during flight was
tested to 2 atm. Electronic subassemblies and critical parts like gas valves were vibration
2
tested using the laboratories facility. E&M tests and temperature tests were made on
subassemblies.
The completed instrument was shipped to GSFC where integrated E&M tests and
exposure to acoustic environment could be carried out in large size test chambers. The
instrument passedall these testswithout requiring any modification.
6. Preflight Performance Tests
Performance tests of the completed instrument are difficult to carry out in the absence
of a beam of relativistic heavy nuclei. The only particles readily available in a laboratory
at sea level are cosmic ray/_-mesons. Increasing the gain of several detectors and their
electronics it is possible to bring the p-meson signals into the range of the instrument
and to carry out rough performance tests. This was done in the laboratory at Chicago
and after shipment at KSFC. Preflight performance tests were complicated by the fact
that the instrument had to be delivered and enclosed in its container more than a year
prior to launch. Onboard electronics therefore became inaccessible and all communications
with the instrument had to be carried out through the GSE and onboard processor. This
required design and construction of a considerable amount of additional electronics, thus
increasing complexity as well as cost. During the flight the MWPCs must be flushed with
the very expensive gas xenon to operate correctly. During the preflight phase this gas was
used at only a few occasions to test proper performance. Maintenance and cleanliness of
the chambers was achieved by continuous flow of an inexpensive gas mixture. The preflight
period with periodic performance tests revealed no major problems and integration into
the spacecraft was achieved without encountering difficulties.
7. Activation, Flight Performance, Data Collection
After an aborted attempt to launch Spacelab-2 in early July 1985, the launch took
place on July 29, and the spacecraft returned on August 5. Activation of the CRN elec-
tronics, gas flush of the MWPC followed the prepared timeline. After 14 hours of flight
the instrument was fully operational, and complete data were received. The first day was
used to optimize parameters like high voltage levels, discriminator levels and the final
choice of the master coincidence. The instrument worked continuously until the end of the
flight. Occasional crashing of the onboard processor could always and rapidly be reset and
caused little loss of data. The cause for these crashes was identified and corrected after
return of the instrument and was found to be due to a hardware timing error. The biggest
loss of data for this experiment, where long exposure is crucial, came through competing
requirements for spacecraft attitude for the different experiments, and the times spent in
the radiation belts due to the choice of a high latitude orbit. Out of a total flight time of
179 hours, only 78 hours were useful to our datataking.
8. Postflight Instrument Check - Present Status
After unloading at KSFC the instrument was trucked back to the University of Chicago
and thoroughly tested. It was found in excellent operating condition. The instrument was
partially disassembledfor safe storageand maintenanceand is awaiting the opportunity
for a long duration flight.
9. Data Analysis and Scientific Results
Data analysis began immediately after return and has extended to the present. A full
account of the scientific results is given in the published papers that are attached and are
part of this report. CRN was an extremely successful experiment which benefited greatly
from the enthusiastic support by the scientists, the technical staff and the management
groups at the University of Chicago, at MSFC and at KSFC.
If one wishes to single out one item for complaint, it is the over-crowded facility that
was made available to the scientific groups at JSC. It is a miracle and testimony to the
scientists' discipline that this apparently did not lead to a major error.
4


Cosmic Ray Nuclei (CRN) detector investigation

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