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Method:
The instrument is placed in a chamber where the ambient temperature is set to values between -10
and +35°C. (These temperature settings cause the internal Brewer temperature monitor to register
between approximately -5 and +40°C.) The temperature is set for 2 hours at +35 °C and then
gradually lowered by approximately 1.1 °C per hour, taking approximately 50 hours in total. A
typical command sequence send to the Brewer during this test period is
PDFR(HP)HGSLSLDTRSAPW2TE100. The HP command is left out for single monochromator
brewers.
After the Brewer has performed the above test sequence over the whole temperature range, the
data is first analysed for operational failures and discrepancies. Special attention is given to the AP
voltages, the *oavg files and the HG wavelength calibration postion right after the FR.
Use the five F() values at all the Brewer temperature settings to determine the five temperature
response coefficients in the following five equations:
F(i)
F
(i)
TC(i)
←
+
0
where
F(i) are the scaled, corrected count rates for slit positions 2 to 6
F
(i) = F(i) at 0 °C
0
TC(i)
is the temperature response coeff. for the i'th operational wavelength
T
is the Brewer temperature in °C.
The values of F0(i) and TC(i) are determined by linearly regressing F(i) against T. By using the
negative of the TC(i) coefficients (as described in Compensating for Temperature under
Preliminary Data Reduction document) the wavelength-dependent temperature response of the
instrument is compensated.
Compare the TC(i) coefficients with those listed in the Final Test Manual. If the freshly determined
values do not agree with those obtained at the factory you should consult KIPP & ZONEN or EC
regarding the advisability of updating the instrument Constants File (CF command). Although the
zero-Celsius values, F0(i), are not used by the Brewer software they should be recorded for future
reference.
Change of Photomultiplier Tube (PMT):
Brewers with serial numbers up to #190 have photomultipliers manufactured by ET Enterprises
Limited of the UK (previously known as Electron Tubes, Thorn-EMI and EMI). These PMTs are no
longer available in a specification that meets the demands of the Brewer.
Brewers with serial numbers #191 and higher are fitted with Hamamatsu photomultipliers. These
have superior performance to the ET tubes, but there is s restriction on the maximum operating
temperature. The Hamamatsu PMT's have an ambient temperature operating range of 0° to +50°
Celsius. When the temperature inside the instrument is higher than 50° Celsius too often, this
could adversely affect the characteristics of the PMT.
Preventive measures are to be taken when the instrument is located at a site where the
temperature inside the Brewer exceeds the limit of 50° Celsius. A simple solution would be to make
a reflective heat shield over the front and top of the white Brewer cover (it could also extend down
the back of the Brewer, but this is not necessary).
The heat shield should have a separation of about 25 mm from the cover, to allow air to circulate
by wind or convection and to transport away the warmth. The heat shield can be made from
104
*
T,
i
2
to
6
=
MKIII OPERATOR'S MANUAL
APPENDIX F FACTORY TESTS
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