Initial definition studies were performed for the SCIN/MAGIC experiment selected as an Astromag investigation on Space Station Freedom. The study focused on Science Objectives and Science Requirement, Accommodation on both the STS and the Astromag facility, Data extraction techniques and Background Studies. The detectors are emulsion chambers which will be exposed for approximately 90 days and then recovered from orbit for subsequent processing and analysis in the laboratory. Such a technique is the only means to obtain information on the ultrahigh energy cosmic rays and their nuclear interactions. The SCIN/MAGIC investigation can supply unique data in relatively unexplored energy region and address many of the fundamental questions in particle astrophysics

Wefel, John P.

English

NASA Technical Reports Server

iv
FINAL TECHNICAL REPORT
 O,)P
Spectra, Composition and Interactions of Nuclei above 10 TeV
Using Magnet-Interferometric Chambers (SCIN/MAGIC)
(Order H- 11204-F)
(Req. 1-O-JA-46002(IF))
Prepared for
National Aeronautics and Space Administration
George C. Marshall Space Flight Center
Huntsville, AL 35812
by
John P. Wefel
Department of Physics and Astronomy
Louisiana State University
Baton Rouge, LA 70803-4001
15 February 1991
(_IA_A-CR-18B21_) SPECTRAv COMPC$1TION AND
INT_RACTIONS OF _UCLLI A6OVF 10 T_V USIMG
MAGNET-INTERF_ROMFTRIC CHAH_ERS (SCIN/MAGIC)
F:in:_l Report (Louisiana State Univ.) IO p
CSCL 20H
N91-24_346
G3/72
Unclas
033031_
https://ntrs.nasa.gov/search.jsp?R=19910015532 2020-03-19T18:05:40+00:00Z
FINAL TECHNICAL REPORT
Purchase Order H- 11204-D
1. Introduction
The "Spectra, Composition and Interactions of Nuclei Above 10 TeV Using Magnet
Interferometric Chambers" (SCIN/MAGIC) experiment was selected for flight as an attached
payload to utilize the Astromag Facility on Space Station Freedom. The investigation has
two aspects. The first experiment involves the use of emulsion chambers to record individual
nuclei in the cosmic radiation at energies above -10 TeV (SCIN) in order to investigate the
composition and the energy spectra of cosmic rays in the energy region above currently
available data, extending into the air shower regime. This is an astrophysically important
region of the energy spectrum which may provide clues to the origin of the highest energy
particles. The second aspect involves using emulsion chambers of a different design in the
field of the Astromag magnet (MAGIC). In this case, the experimental goal is to study the
high energy nuclear interactions of the cosmic ray particles. For each event that interacts, the
secondary particles will be deflected in the magnetic field permitting the charge and the
rigidity to be measured. This permits analysis of n+, r_" correlations and searches for heavier
particles produced in the interaction. Since such interactions are the current basis for
measurements of cosmic rays at the highest energies, the results will, undoubtedly, improve
our understanding of this fundamental process.
The SCIN/MAGIC program in the US is a collaboration between MSFC, Louisiana
State University (LSU), University of Alabama in Huntsville _AH) and University of
Washington in Seattle (UW). The team is lead by T. A. Parnell from MSFC who directs the
overall project and supervises the work of the university co-investigators.
This purchase order covered the initial effort at LSU directed towards a Definition of the
SCIN/MAGIC project for the space station office. The principal objectives were the
development of Science Requirements, Experiment Accommodation, Instrument
Requirements and Analysis Planning. The SCIN/MAGIC experiment is unique in that it
involves visual detectors, nuclear emulsions, x-ray films and etched plastic track detectors,
which must be recovered from SSF for subsequent processing and analysis in the laboratory.
This requires that the detector materials be developed and tested to withstand the
anticipated environment, both pre-launch, on the station and return to Earth, requiring
detailed materials testing and packaging. Further, the science data is obtained only after the
space exposure, return to Earth and processing in the laboratory. SCIN/MAGIC data
acquisition commences some 6-12 months after the initial launch of the modules and requires
2-3 years to complete. Thus, detailed analysis planning and analysis equipment development
must be an early and integral part of the SCIN/MAGIC investigation plan. Each of these
areas was studied by LSU during the initial effort covered by this purchase order.
2. Science Objectives
The goals of the SCIN portion of the overall investigation have been refined during this
period. One of the basic purposes of the investigation is to extend the region of directly
measuredparticle spectraupward in energy. Figure 1 illustrates this for the Hydrogen
(proton) component, the most abundant species among the cosmic rays. Plotted is a
summary of previous measurements of the differential energy spectra including the recent
balloon results from the JACEE experiments at _he highest energy.
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Figure 1. Compiled differential energy spectra for
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The current measurements extend to -2.5 x 107 MeV (25 TeV) with reasonable statistics
and join smoothly to the lower energy results. The SCIN/MAGIC program must be capable
of reducing the uncertainties on the data at 5-25 TeV and extending the measurements, with
good statistics, to at least 100 TeV.
Figure 2 shows the compilation of the all particle cosmic ray spectrum as deduced from
direct measurements at low energies and from air shower observations at higher energies.
Note that there is a feature in the spectrum at -1015 eV (1000 TeV) beyond which the slope
of the all-particle spectrum changes. The SCIN exposure for extended periods in space is
designed to push the direct measurements as close to this feature as possible to search for
the beginning of the spectral change. Thus, repeated exposure of SCIN chambers may be
necessary to carry out this objective. It is recommended that such a multi-exposure plan be
incorporated into the overall investigation scenario.
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Turning to the multiply charged nuclei, Figure 3 shows a compilation of recent data on
the proton to helium (p/o0 ratio. The highest energy point was measured at several
TeV/nucleon and shows an anomalously low value, compared to the lower energy data. Since
the proton results (Figure 1) show no suppression, this effect is due to an increased helium
flux at TeV energies, a possible indication of new physics at the high energies to be studied
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Figure 3. Compiled data for the H/He ratio as a function of energy
by SCIN/MAGIC. Such composition effects may be related to the (unknown) astrophysics
thatcausesthe"feature"inFigure2. The reducedp/ctratiomeasured by theballoon
experimentsmust be conf'u'medand,moreover,themeasurements must be extendedtocover
a largerenergyrangeto searchforan energydependenceintheratioabove a few TeV. This
becomes an importantobjectivefortheSCIN/MAGIC investigation.
The compositionof thecosmicraysisknown tobe energydependent.In particular,
secondarytoprimaryratiosdecreasewith increasingenergy,indicatingthattheparticles
pass throughlessinterstellarmatterathigh energies.One of theimportantoutstanding
questionsiswhether thisdecreasingmattertraversalcontinuesto thehighestenergies.
Figure4 shows a compilationofdatafortheB/C ratiowhich illustratestheenergy
dependence. The recenthigh energymeasurements areshown as verticalrectangles,and the
upper limitatthehighestenergyreferstodataat-I TeV/nucleon. There isno evidencefora
flatteningof theB/C ratiowithincreasingenergy,butsuch a flatteningata mattertravcrsalof
I-2g/cm2 cannotbe ruledoutwith currentexperimentalresults.Ifthemattertraversaldoes
reacha finitelimit,theneven thehighestenergyparticlesmust passthroughsome
interstellarmatterwhich impliesthenecessityof correctingthecompositionforfragmentation
in theinterstellarmedium. Iftheratiocontinuestodecrease,thenatthehighestenergiesit
shouldbe possibletoobservethesourcecompositiondirectly.
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Figure4. Compiled datafortheenergydependenceof theB/C ratio.
The experimental challenge for the SCIN/MAGIC investigation is two-fold. First,
sufficient statistics for Carbon nuclei must bc collected to allow, at least, a reliable upper limit
to be placed upon the B/C ratio at energies of 5-10 TeWnuclcon. Second, the charge
resolution of the SCIN/MAGIC detectors must be demonstrated to be sufficient to separate
any (few) Boron events that arc observed from the "tail" of the Carbon distribution.
Another important region is the iron peak. Here, measurements extend to 1-2
TeV/nucleon and show that the iron spectrum is flatter (7-2.55) than the spectra of other
primary elements (T~2.7). At higher energies, only upper limits are available. If all of the
cosmic ray heavy nuclei are accelerated by the same source or sources, then the spectra
should be same, when the particles leave the acceleration region. These source spectra are
then modified by the propagation of the particles in the galaxy. In this picture the iron
spectrum should begin to steepen at some energy and eventually become a 7-2.7 spectrum.
If this does not occur, then the whole acceleration model for cosmic rays would be called into
question.
Thus, the iron spectrum is a very important measurement for the SCIN/MAGIC
experiment. This is, perhaps, the most stringent experimental requirement since achieving
this objective will require both a large collecting power to obtain sufficient iron events, good
energy resolution for the measured events and excellent charge resolution to separate iron
from the sub-iron secondaries. The latter will require detailed detector specifications, quality
control during production and careful environmental control before, during and after the
exposure in space.
3. Accommodation of SCIN/MAGIC
The SCIN/MAGIC payload is to be carried to orbit by the STS, deployed to SSF and
then attached to the Astromag facility either by Astronauts or by the station robotic servicing
system. This provides two accommodation questions: (1) Orbiter accommodation and (2)
Astromag attachment.
The transport of emulsion chambers in the orbiter cargo bay involves the emulsion
chamber "box" and its attachment to the structure, for example an MPESS type system. This
problem is being investigated by the UAH group under contract to NASA, working with
MSFC staff. Under this program a "box" and a carrier system are being developed.
MAGIC
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Figure 5. Proposed configuration for SCIN/MAGIC
attached to Astromag.
For theAstromagaccommodation,the questionis the configurationof the MAGIC
emulsionchamberwithin thefield of theAstromagmagnet.The initial configurationproposed
for theexperimentis shownin Figure 5. Note that thechambersaremountedin the upper
regionof thefield producedby themagnet. TheAstromagis a "singlecoil" systemso that
thefield is strongestnearthe faceof thecoil anddivergeswith distancefrom thecoil.
Obtaining themaximumbendingandthebestrigidity resolutionin the MAGIC chambers,
requiresa mountingascloseto themagnetfaceaspossibleandin the centralregionof the
field. It is recommendedthatthe "box" bedesignedto havea minimum thicknesson theside
next to the magnetcoil and that anAstromagaccommodationbe investigatedthat placesthe
centerof theMAGIC drift spacesnearthecenterline of thecoil.
4. AutomatedMicroscopy
A major factorin the successof theSCIN/MAGIC programwill be thedegreeto which
the eventmeasurementprocesscan beautomatedto allow both an increasein measurement
speedand the useof lesswell-trainedpersonnelto performmanyof the measurements.
Automatedmicroscopy,or at leasta semi-automatedsystemwill be neededto meet this
requirement. Automatedsystemsareavailablecommercially,but designedfor specific
applications,e.g. analysisof biological specimens,inspectionof microelectronicssubstrates,
etc. Suchsystemsare, in general,too limited for thevarietyof problemsencounteredin
emulsionanalysis,which is inherentlythree-dimensional.Rather,onecaneither build a
customsystemor beginwith a commercialproductandmodify it for the presenttask. Both
approachesarebeing studiedby the SCIN[MAGIC collaboration.
At LSU, we are developing a custom system based upon a CCD camera mounted on a
microscope with a digitized stage. This is a semi-automated system developed for use in
accelerator beam experiments. The system is controlled by an 80386 microcomputer, which
could easily handle control of the stage motion if stepper motors were attached to the stage.
The CCD image is of high quality and can be used to automate some of the measurement
process.
For use with SCIN/MAGIC, however, the incident particle trajectory will vary over a
large angular range (compared to an accelerator beam), and this will necessitate changes in
procedures and in the event reconstruction software. A first step has been taken in the latter
area by developing a reconstruction program for events in emulsion chambers. An example is
shown in Figure 6 for a JACEE event from a balloon-borne emulsion chamber. Figure 6
shows a three-dimensional plot of the secondary tracks emerging from the interaction
occurring at the origin of the coordinate system, with the primary particle incident from the left
along the Z-axis. Dimensions are in micro-meters and illustrate the fiducial volume that must
be examined microscopically to find and separate all of the secondary particles. In the case of
a MAGIC chamber, many of these particles would show a curvature that would be fit to
indicate the particle's rigidity.
The current software development is a beginning and shows that semi-automated
microscopy is possible for a SCIN/MAGIC program. The nature of the problems is well
understood, but significant effort will be necessary to turn the current level of software into a
fully functioning system for SCIN/MAGIC analysis. It is recommended that this development
effort be continued, with increasing resources, over the next several years.
\
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JACEE EVENT KlO
Figure 6. Software reconstruction of a IACEE emulsion chamber event.
5. Background Measurements
One of the principal differences between a space exposure and a balloon experiment is
the higher level of low energy background tracks, even in the SSF orbit. These are due to the
penetrating protons encountered in the South Atlantic Anomaly region of the orbit. This
background may limit the exposure time for emulsion chambers in space or dictate the degree
to which ultra-high energy events can be analyzed in the exposed chambers. The latter
problem can be evaluated from balloon experiments flown near the magnetic poles, so that the
chambers experience a large "dose" of low energy events along with the ultra-high energy
particles that are the main goal of the SCIN/MAGIC program.
Under this contract we have participated in such a test by including several small
emulsion chambers on a payload launched from Antarctica in December, 1990. The flight
lasted -8.5 days completing one circumnavigation of the South Pole. The package was
successfully recovered and returned to the US for development and analysis. Test plates
have been developed and show that the detector materials survived the exposure quite well.
Processing of the full stack is in progress and the materials will be analyzed over the next
several months. The results will be extremely important for the final design of the
SCIN/MAGIC chambers and for the "box" that holds the photosensitive materials.
6. Reference
"Spectra,Compositionand Interactionsof Nuclei with Magnet InteractionChambers,"
T. A. Parnell,T. H. Burnett,M. L. Cherry,S.Dake,J.H. Derrickson,W. F. Fountain,M.
Fuki, J.C. Gregory,T. Hayashi,R. Holynski,J. Iwai, A. Jurak,J.J. Lord, O. Miyamura,K.
Niwa, H. Oda,T. Ogata,F. E. Roberts,T. Shibata,S. C. Strausz,T. Tabuki,T. Taira, Y.
Takahashi,T. Tominaga,J.W. Watts,J.P.Wefel, B. Wilczynska,H. Wilczynski, R. J.
Wilkes, W. Wolter, T. Wosiek,A. Yamamoto,H. Yokomi andT. Yuda, in Particle
Astrophysics, eds. W. V. Jones, F. J. Kerr and J. F. Ormes, AlP Conf. Proceedings No. 203,
(New York, 1990, American Institute of Physics), p. 89.
!i ,,m lli I
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4. TTtlearielSub,de
Report Documentation Page
m
2. _,_ A_n No.
........ L ............
Spectra, Composition and IHteractions of Nuclei above
i0 TeV Using Magnet-Interferometric Chambers (SCIN/MAGIC)
• 1. Author(sl '
John P. Wefel
|
9.P_'ormingOrganizatlon Name andAddrels
Louisiana State University
Department of Physics & Astronomy
Baton Rouge, LA 70803-4001
12. Sporc, orir_g Agq_'y NIIf_ MKI.Addretl
National Aeronautics and Space Administration
Washington, DC 20546-0001
George C. Marshall Space Flight Center
Huntsville, AL 35812
1IS.Su_ementm-f Noum
-'_._."I_¢_,_;-_._ No.
• s. Dm
15 February 1991
0. _'fom_'_ Oqla_izat_ Code
8. Plrfonlliflg Organization Report No.
115-30-5157-F
10.Woct UnitNo.
1I. Conuict or Grant No.
H- 11204-F
13. TyI_ Reign and PeriodCov_d
Final Technical
11/1/90 - 1/31/91
=m
Initial definition studies have been performed for the SCIN/MAGIC experiment selected
as an Astromag investigation on Space Station Freedom. The study focused on Science _
Objectives and Science Requirements, Accommodation on both the STS and the Astromag
facility, Data extraction techniques and Background Studies. The detectors are emulsion
chambers which will be exposed for -90 days and then recovered from orbit for subsequent
processing and analysis in the laboratory. Such a technique is the only means to obtain
information on the ultrahigh energy cosmic rays and their nuclear interactions. The
SCIN/MAGIC investigation can supply unique data in relatively unexplored energy region
and address many of the fundamental questions in particle astrophysics.
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nuclear interactions/Ast romag/
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Spectra, composition and interactions of nuclei above 10 TeV using magnet-interferometric chambers (SCIN/MAGIC)

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