STJ Quick Start Guide v 2.01
April 1, 2021
Page 16
MCA
These settings control the output scaling of the energy measurement, which correspond to the X-axis
scaling and granularity in the MCA panel.
•
We recommend always using the maximum Number of Bins: 8192 bins
•
We recommend using MCA Bin Width = 0.25 eV/Bin with a 2 keV Dynamic Range. If you are
interested in energies above 2 keV, increase both of these settings by factors of 2, e.g. 0.50
eV/Bin with 4 keV Dynamic Range, etc.
BASELINE
The Baseline Average setting determines the number of samples in the running baseline average.
•
We recommend always using the default value: 256 Samples, unless otherwise instructed by
XIA
ADVANCED SETTINGS
Additional acquisition settings are accessible in the Edit Filter Parameters dialog, including the slow filter
Gap Time, the Peak Capture method and Fast Trigger Filter settings. Please refer to the
for more details about these settings.
•
Press the Edit Filter Parameters button to edit the advanced acquisition settings
•
Edit the Gap Time such that the value comfortably exceeds the rise time of incoming pulses as
viewed in the Scope panel. Note that the maximum Peaking Time plus Gap Time are
constrained by the Decimation, i.e. firmware (FDD) file, as described in the
•
We recommend always using the Peak Sensing Capture Method! This means that the largest
energy value within an appropriate window is recorded, which always yields the optimum
energy resolution. With the Peak Sampling method, you will need to adjust the Peak Sampling
Time to achieve optimal energy resolution.
•
We recommend setting the Fast Trigger Filter Peaking Time to 1.000
µ
s for most STJ systems,
which achieves a good balance between speed and noise rejection.
•
The Max Width setting controls pileup rejection in the Fast Trigger Filter: pulses that remain
over threshold for longer than this interval are rejected. This setting should normally be set to
a conservative 10
µ
s. For high count rates (>100 kcps), you may want experiment with reducing
this value to reject events that pile up in the Fast Trigger Filter.
BIASSCAN PANEL
The BiasScan panel is used to plot the STJ I-V curve in order to select a bias voltage for the detector. When
the “Start Scan” button is pushed, the bias voltage for each STJ detector is set to the “Starting Offset”
value, then the voltage is incremented across the prescribed voltage range. At each increment the output
voltage and signal noise level are measured. The output voltage is proportional to the detector current. It
is plotted in green, with arbitrary units on the left-hand y-axis (Note that we intend to update the
software with y-axis units in Amperes). The noise level is plotted in arbitrary units on the right-hand y-
axis.
