Thomas Hams

Astrophysics Science Division
NASA/GSFC
Code 661, The Astroparticle Physics Laboratory
Greenbelt, MD 20771

tel: 301-286-2088
fax: 301-286-1682
e-mail: thomas.hams-1 @ nasa.gov

Present Position

Research Sceintist, USRA

Brief Bio

After earning his the physics degree at the University of Siegen, Germany in 1996, Mr. Hams jointed their Astrophysics group as a research assistant. There he got involved with the ISOMAX experiment, a balloon-borne superconducting magnetic-rigidity spectrometer, capable of measuring the isotopic composition of the light elements (Z<8) in the galactic cosmic radiation up to 5 GeV/c and in particular the radioactive clock-isotope 10Be. In ISOMAX, Mr. Hams was responsible for the drift-chamber tracking detector of the spectrometer, which was Siegen’s contribution to the experiment. He supported two balloon campaigns of ISOMAX, in 1998 and 2000. His work on ISOMAX 1998 flight was the topic of his PhD thesis. He received he degree in early 2002.

The same year, Dr. Hams was awarded an National Research Council Fellowship at GSFC, where he joined the BESS collaboration, which is a US-Japanese effort in search of antimatter in the cosmic radiation using a balloon-borne spectrometer. He analyzed BESS-1999 data and investigated the use that instrument for measuring the electron flux up to 20 GeV.

For BESS-Polar, Dr. Hams initially developed, integrated, and tested pressurized Photomultiplier assemblies, which allowed the PMTs in the Aerogel Cherenkov Counter (ACC) to operate in near vacuum. He took the initiative and assumed responsibility for the entire ACC detector, including developing and testing the counter box design and a mounting technique for the Aerogel blocks. In addition, Dr. Hams supported the fabrication of the Time-of-Flight (TOF) counter and the testing of the associated readout electronics both GSFC responsibilities in BESS-Polar and provided support to the visiting Japanese collaborators in the overall BESS-Polar integration effort at GSFC. He took the initiative and assisted in the GSFC instrument management and oversaw technicians and student works. He was involved in the BESS compatibility test in Palestine, TX und supported the in-flight instrument monitoring during BESS-Polar’s successful first flight launched from the US-Antarctica Station in McMurdo in late 2004.

After the flight, Dr. Hams analyzed the flight data of the Cherenkov Counter. In late 2005, he conducted an accelerator test at KEK, Japan, which verified the flight performance of the ACC, showing a lower than expected rejection power based on previous BESS Cherenkov counters. He conducted a detailed investigation of optical material properties used in the light diffusion volume and wrote a GEANT4 simulation code of Cherenkov counter. This study revealed that the larger number of individual Aerogel blocks resulting from a size limitation in the manufacturing introduced additional photon absorption and thus reduced the performance of the counter. This finding lead to the decision to acquire new, larger Aerogel blocks to overcome this effect in the second flight.

Dr. Hams is currently working on the preparation of BESS-Polar for its second flight from Antarctica scheduled for late 2007. His responsibilities include the fabrication and testing of improved ACC and the TOF systems, and to adapt the TOF photomultiplier tubes to the hermetic assemblies. He is also developing a GEANT4 simulation for the scintillator to optimize the shape of the light guide for the new TOF counter.

2005-present Research Scientist at USRA
2002-2005 Resident Research Associate at NAS/NRC
1999-2002 Postdoctoral Research Position in Astrophysics Group at the University of Siegen, Germany
1995-1999 Research associate in Astrophysics Group at the University of Siegen, Germany
1987-1990 Electronics Engineering Technician Apprenticeship at Theo Benning, Bocholt, Germany

Educational Background

2002 Ph.D., Physics, University of Siegen, Germany (Measurement of the isotopic ratios in the elements lithium beryllium, and boron up to energies of 1.3 GeV/nucleon in the galactic cosmic rays using the balloon-born superconducting magnet spectrometer ISOMAX1998)

1996 Diplom-Physiker (equivalent to M.S.), University of Siegen, Germany (Development of a drift camber gas system and test of a low-power drift chamber readout for the ISOMAX experiment)

Research Interests

Experimental High Energy Astrophysics, Cosmic-Ray Antimatter Search, and Experimental Techniques in Particle Physics.

Current Projects

BESS (US–Japanese balloon-borne antimatter magnetic spectrometer). The best up-to-date operating instrument to measure cosmic-ray antiprotons. My contribution to BESS-Polar includes the design, fabrication, and testing of the Aerogel Cherenkov Counter as well as analysis of the flight data. To this point BESS-Polar is beeing reworked for its second flight scheduled for late 2007.

Selected Publications

Mitchell, J.W. et al. 2005, Advances in Space Research 35 (2005) 135-141, "Precise measurements of the cosmic ray antiproton spectrum with BESS including the effects of solar modulation"

Yoshida, T. et al. 2004, Advances in Space Research 33 1755-1762, "BESS-polar experiment"

Hams, T. et al., 2004, Astrophysical Journal, 611, 892, "Measurement of the Abundance of Radioactive 10Be and Other Light Isotopes in Cosmic Radiation up to 2 GeV Nucleon-1 with the Balloon-borne Instrument ISOMAX"

Haino, S. et al. 2004, Nucl. Inst. Meth. A 518, 167-171, "Progress of the BESS Superconducting Spectrometer"

Nozaki, M. et al. 2004, Nucl. Inst. Meth B 214, 110-115, "BESS-Polar"

Mitchell, J.W. et al. 2004, Nucl. Phys. B 134, 31-38, "The BESS Program"

Hof, M. et al. 2000, SAMBA 99-Symposium, published in NIM A 454, 180, "ISOMAX: A Balloon-Borne Instrument to Cosmic Ray Isotopes"

Conference Papers
Matasuda, S. et al., 2005, 29th International Cosmic Ray Conference (Pune) 3, 25-28, "Observation of low energy antiprotons at the 2004 BESS-Polar fight in Antarctica"

Yoshida, T. et al. 2005, 29th International Cosmic Ray Conference (Pune) 3, 33-36, "The 2004 BESS-Polar scientifc fight in Antarctica"

Hams, T. et al. 2005, 29th International Cosmic Ray Conference (Pune) 3, 69-72, "Flight Performance of the BESS-Polar Aerogel Cherenkov Counter"

Sasaki, M. et al. 2005, 29th International Cosmic Ray Conference (Pune) 3, 421-424, "Low Power Front-End Electronics for the BESS-Polar Time-of-Flight Counter and Aerogel Cherenkov Counter"

Yoshida, T. et al. 2003, Proc. 28th International Cosmic Ray Conference (Tsukuba), 2081-2084, "BESS-Polar Experiment"

Hams, T. et al. 2003, Proc. 28thInternational Cosmic Ray Conference (Tsukuba), 1813-1816, "Measurement of electron spectrum to high energies with the BESS-1999 experiment"

Göbel, H. et al. 2001, 27th International Cosmic Ray Conference (Hamburg), 5, 1663, "The measured ratio of Lithium isotopes in cosmic rays in the energy range from 0.2 to 1.3 GeV/nucleon with the ISOMAX 98 instrument"

de Nolfo, G.A. et al. 2001, 27th International Cosmic Ray Conference, (Hamburg), 5, 1659, "A measure of 10Be/9Be ratio above 1 GeV/nucleon: Results from the 1998 Flight of ISOMAX"

Hams, T. et al. 2001, 27th International Cosmic Ray Conference (Hamburg), 5, 1655, "10Be/9Be ratio up to 1.0 GeV/nucleon measured in the ISOMAX 98 balloon flight"

de Nolfo, G.A. et al. 1999, 26th International Cosmic Ray Conference, Salt Lake City (USA), 3, 29, "Cosmic-Ray Isotope Measurements using the Cherenkov-Rigidity Technique in ISOMAX"

Geier, S. et al. 1999, 26th International Cosmic Ray Conference (Salt Lake City), 3, 117, "In-flight Performance of the ISOMAX TOF"

Mitchell, J.W. et al. 1999, 26th International Cosmic-Ray Conference (Salt Lake City), 3, 113, "ISOMAX Flight Performance of the Isotope Magnet Experiment"

Hams, T. et al. 1999, 26th International Cosmic Ray Conference (Salt Lake City), 3, 121, "The ISOMAX Magnetic Rigidity Spectrometer"

Publications at the ADS website.