Properties of plasma radiation diagnostics Page: 5 of 19
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to UNT Digital Library by the UNT Libraries Government Documents Department.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
on Long Island, New York. Even when carefully prepared the cathode surface will show signs of carbon
contamination (see Fig. 1). Once used the cathodes are often visibly contaminated and we have seen the
response shift by factors of 2-3. Our experience has shown a cathode to cathode response variation of
about 15% within a given batch of new aluminum cathodes. By discarding the detector after use we are
not required to protect the XRD-96 with massive debris shields, fast-closing valves, fast bias voltage
dump electronics, etc. and their associated high costs. This allows us to use large numbers of detectors at
any many locations in our experiments. Being a photoemissive detector very small amounts of surface
contamination can dramatically change the response of a photocathode since the typical range of
photoelectrons can be measured in tens of angstroms. This extreme contamination sensitivity led us
explore alternative detector technologies.
SILICON PHOTODIODES
Recent advances in fabrication technique have made the silicon photodiode detector attractive for
soft x-ray experiments. Unlike older silicon photodiodes the vacuum ultra-violet detectors made by
International Radiation Detectors6 (IRD) are fabricated without a dead layer and a passivating layer only
60 angstroms thick. These features allow the new silicon photodiodes to be used at photon energies well
below 100 eV. Other advantages of silicon photodiodes include low bias voltage (0 - 50 volts),
insensitivity to surface contamination, long term stability, nominally flat response, fast rise time, ability
to use very thin x-ray filters deposited directly onto the diode surface, and small size. These features
have lead the National Institute of Standards and Technology (NIST formerly NBS) to the adoption of
the IRD detectors as secondary standards for soft x-ray work.
We are currently using our beamlines at the NSLS to characterize the IRD type HS-1 detectors
between 30 eV and 10 keV x-ray energy. In addition a visible light monochromator provides calibration
data from 1 to 4.5 eV. Our visible measurements have confirmed the manufacturers claim of less 5%
response variation between diodes and preliminary analysis of x-ray measurements also appears in
agreement. Measured response values overlaid with a calculated response are shown in Fig. 2. The
deviation from a nominally flat response in the visible and above 700 eV is due to our usage of the HS-1
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Idzorek, G.C. & Oona, H. Properties of plasma radiation diagnostics, article, June 1, 1996; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc671250/m1/5/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.