The Super-TIGER Instrument to Probe Galactic Cosmic Ray Origins

J.W. Mitchell, NASA Goddard Space Flight Center

for the Super-TIGER collaboration

Washington University, St. LouisGoddard Space Flight CenterCalifornia Institute of TechnologyUniversity of Minnesota

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Super-TIGER CollaborationW.R. BINNS2, R.G. BOSE2, D.L. BRAUN2, E.R. CHRISTIAN1, W.M. DANIELS1, G.A. DE NOLFO1, P.F. DOWKOTT2, D.J. HAHNE1, T. HAMS1,a, M.H. ISRAEL2, J. KLEMIC3, A.W. LABRADOR3, J.T. LINK1,b, R.A. MEWALDT3, J.W. MITCHELL1, P. MOORE2, R.P. MURPHY2, M.A. OLEVITCH2, B.F. RAUCH2, F. SAN SEBASTIAN1, M. SASAKI1,c, G.E. SIMBURGER2, E.C. STONE3, C.J. WADDINGTON4, J.E. WARD2, AND M.E. WIEDENBECK5

1 NASA/Goddard Space Flight Center, Greenbelt, MD 20771 USA 2 Washington University, St. Louis, MO 63130 USA 3 California Institute of Technology, Pasadena, CA 91125 USA 4 University of Minnesota, Minneapolis, MN 55455 USA5 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 USA

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Scientific Motivation• GCR origin still not determined – Ultra-heavy (Z≥30) GCR

abundances can provide key information• Trans-Iron Galactic Element Recorder (TIGER) results:

– GCRs originate from the core of super-bubbles, where OB associations enrich the ISM with massive star outflow (WR phase & SN)

– GCR acceleration favors elements found in interstellar dust grains

– Acceleration of volatile & refractory elements follow a mass dependence of ~An (n ~2/3 for refractory elements and n~1 for volatile)

• TIGER results complement ACE measurements of 22Ne, 58Fe/56Fe, C/O, N/O, N/Ne.

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Results from 50 days of TIGER

10 20 30 40 50 60 70 80 90100

0.1

1

Volatile Refractory

GC

RS

/(8

0%

SS

+2

0%

MS

O)

Atomic Mass

Mg

Al

Si

P

Ca Fe

Co

Ni

Sr

N

Ne

SAr Cu

Zn

Ga

Ge

Se

Refractories

Volatiles

6.9.10_Figure_for_MHI/TIG_GCRS_vs_80-20mix_rev2

TIGER had excellent charge resolution. But limited statistics. TIGER recorded 10 events in the peak at Sr.

Fe

Ni

Zn

Note resolved peak at Ga only 10% as high as Zn.

Ge Se Sr

Super-T adds refractory Zr & Mo (A=91&96) and volatile Kr & Rb (A = 84 & 86) .Combined TIGER & Super-TIGER will have statistical errors smaller by factor ~3.

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Measurement Objectives• Primary Objective: sensitive test of GCR origin

− Abundances of individual UH elements 30 Z 42− Exploratory measurements up to Z 56 − Test of OB-association source model− Test of A-dependence of acceleration

• Secondary objective: search for evidence of microquasars− Energy spectra of elements 10 Z 28

• UH elements are rare – need many times TIGER statistics− Large collecting area (5 m2).− Large exposure - planned flights in December 2012 & 2014

from Antarctica (~60 days total)

− 7 to 8 times TIGER statistics.

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Super-TIGER InstrumentHodoscopeScintillator

Aerogel Cherenkov

Acrylic Cherenkov

Scintillator

ScintillatorHodoscope

•Two nearly identical modules− One module has aerogel with refractive index

1.045. The other has half 1.045 and half 1.025− Energy resolution to 10 GeV/nucleon

•Each module is the size of two TIGER instruments. − Total active area 5.4 m2

•Custom low-power electronics− Each PMT pulse-height analyzed− Individual HV control

•Areal density in instrument aperture has been minimized to reduce particle loss to interactions− Rohacell substrates replace

gatorfoam panels used in TIGER for all detectors

− Reduce thermal insulation on top of instrument

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Charge Determination Technique

dE/dx-CherenkovdE/dx=kZ2/2

C1=k’Z2 [1/(1-n12/2)]

Cherenkov-CherenkovC0=k’Z2 [1/(1-n0

2/2)]C1=k’Z2 [1/(1-n1

2/2)]

• Nominal charge threshold set for Z=10• Dynamic range Z=10 to 56

Super-TIGER Payload

• Mechanical design for minimum weight - fly on 40MCF-light balloon

• High Gain Antenna (HGA) and rotator– Telemeter all or nearly all data to

ground– Reduces cost and complexity of PV

system • Recovery with Twin Otter or Basler

4.28 m (14.0 ft)3.37 m (11.1 ft)

1.83

m (6

.0 ft

)

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Super-TIGER vs. TIGER

• Detector area 4x that of TIGER, while height ~same.• Fewer interactions in detector due to thinner structural

components.• Effective geometric acceptance, accounting for

interactions, is ~6.4x that of TIGER.• Super-TIGER flights to take place ~eleven years after the

TIGER flights (2001, 2003), so ~same level of solar modulation (possibly less).

• With 60 days of Super-TIGER, added to 50 days of TIGER, combined data set will have ~8.7 x TIGER events.

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Expected Numbers of Events

• From two 30-day Super-TIGER flights (based on numbers seen by TIGER for Z 38 and based on HEAO-C3 + Ariel even-Z estimates for Z>38)

28 30 32 34 36 38 40 42

1

10

100

Num

bers

of E

vent

s

Charge

Assumed =0.23 cu; 7.7 x TIGER

Monte Carlo estimate of total numbers of events

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Super-TIGER Status

• Detector fabrication in progress• Electronics fabrication/test nearing completion• Gondola fabrication in progress.• Design of shipping GSE beginning.• Schedule:

– Instrument/Payload I&T - December 2011 to May 2012.– Thermal-Vacuum Tests (NASA Glenn) - May 2012– Mission integration (CSBF Palestine, TX) July - August 2012– Shipment to Antarctica - September 2012– Pre-flight I&T – November 2012– Flight – December 2012

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Summary

• Super-TIGER will measure UH nuclei up to Z=42 with exceptional statistical accuracy (exploratory observations through Z=56).

• Precise measurements of energy spectra of 10 ≤ Z ≤ 30 from 0.8 to 10.0 GeV/nucleon

• On track for first flight December 2012!• See posters 16-17 August for details:

−Hodoscope - OG1.5 714 Ward, J.E. −Scintillators – OG1.5 737 Link, J.T.−Cherenkov – OG1.5 831 Hams, T.