May 17, 2006

2006 NSLS-CFN Joint Users' Meeting Workshop

Vacuum Ultraviolet Radiometry

As part of the 2006 NSLS/CFN Users' Meeting, an all-day workshop on the topic of Vacuum Ultraviolet (VUV) Radiometry was held at Brookhaven National Laboratory on May 17 to address NSLS users with an interest in absolute photon rate measurements. For the purposes of this workshop, the VUV range was defined broadly as the range of photon energies requiring ring-contiguous vacuum (5-5000 eV). Also, both absolute (i.e. radiometry) and relative (e.g. reflectometry) instrumentation and results were discussed. The workshop included presenters from some of the world's most capable synchrotron-based radiometry facilities, including PTB at BESSY-2, ALS / CXRO, SURF-III at NIST, and both facility and Participating Research Team beamlines at NSLS. There were 8 speakers and roughly 45 total attendees. Speakers included Franz Weber (Livermore), Rob Vest (NIST), John Seely (NRL), Frank Scholze (PTB), Steve Hulbert (NSLS), Eric Gullikson (ALS), Tony Kuczewski (NSLS) and Jeff Keister (NSLS).

The major themes of this workshop included applications of absolute VUV radiometry (including fusion research, EUV lithography, astrophotometry, and synchrotron instrumentation), discussion of limitation of various detectors used for absolute radiometry (including cryogenic calorimeters, silicon photodiodes, and other devices), and discussion of VUV beam conditions suitable for radiometry (e.g. calculable synchrotron white light output, monochromatic beam purity and wide energy range).

Application of the various detector and beamline methods to more general beamline science and optical characterization was also covered, with many users interested in applying these tools to beamlines at NSLS and/or NSLS-II. Several groups made note of the damage observed on silicon photodiodes under VUV illumination and it was generally agreed that this damage affects the topmost silicon material. Limitations to the calibration and responsivity of various types of silicon photodiode at different photon energies were also discussed.

The workshop was successful in generating open discussion of beamline techniques and detector limitations among the participants, and gave visitors an opportunity to visit the metrology beamlines at NSLS. The collaborative atmosphere was encouraging, and a similar workshop will hopefully be organized again at Brookhaven, possibly at a future NSLS Users' Meeting.

FOR MORE INFORMATION
Jeff Keister
SFA, Inc.
Brookhaven National Laboratory
Upton, NY
Email: jkeister@bnl.gov