<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <!--Converted with LaTeX2HTML 98.1p1 release (March 2nd, 1998) originally by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds * revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan * with significant contributions from: Jens Lippmann, Marek Rouchal, Martin Wilck and others --> <HTML> <HEAD> <TITLE>PMT Voltage</TITLE> <META NAME="description" CONTENT="PMT Voltage"> <META NAME="keywords" CONTENT="vol2"> <META NAME="resource-type" CONTENT="document"> <META NAME="distribution" CONTENT="global"> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <LINK REL="STYLESHEET" HREF="vol2.css"> <LINK REL="next" HREF="node645.html"> <LINK REL="previous" HREF="node643.html"> <LINK REL="up" HREF="node640.html"> <LINK REL="next" HREF="node645.html"> </HEAD> <BODY > <!--Navigation Panel--> <A NAME="tex2html9551" HREF="node645.html"> <IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next" SRC="icons.gif/next_motif.gif"></A> <A NAME="tex2html9548" HREF="node640.html"> <IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up" SRC="icons.gif/up_motif.gif"></A> <A NAME="tex2html9542" HREF="node643.html"> <IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous" SRC="icons.gif/previous_motif.gif"></A> <A NAME="tex2html9550" HREF="node1.html"> <IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents" SRC="icons.gif/contents_motif.gif"></A> <BR> <B> Next:</B> <A NAME="tex2html9552" HREF="node645.html">Gain steps</A> <B> Up:</B> <A NAME="tex2html9549" HREF="node640.html">Additional information</A> <B> Previous:</B> <A NAME="tex2html9543" HREF="node643.html">Measuring aperture</A> <BR> <BR> <!--End of Navigation Panel--> <H3><A NAME="SECTION003262400000000000000"> PMT Voltage</A> </H3> When photomultipliers are used, the spectral response depends in a complicated way (involving several different phenomena) on the electrode potentials in the first few stages. If the high voltage is changed to vary the gain, as is sometimes done in DC or CI work, the spectral response varies. This must be treated exactly like a variable measuring aperture: only data taken under constant conditions should be reduced together, but sometimes this can be done if adequate calibration data have been measured. <P> The column label is PMTVOLTS. Once again, because several complex effects are involved, the effects are not predictable, so there is no point in trying to use quantitative values. Besides, the voltage settings on many power supplies are not very accurate, nor can one read an analog voltmeter precisely enough to obtain useful numbers. The values in this column will be treated as strings rather than converted to numbers. <P> <BR><HR> <ADDRESS> <I>Petra Nass</I> <BR><I>1999-06-15</I> </ADDRESS> </BODY> </HTML>
