Method and Apparatus for Evaluating Superconducting Tunnel Junction Detector Noise Versus Bias Voltage

The method of claim 26 wherein the control logic in the DXP that measures the standard deviation (σFI) of captured values of FI as a function of bias voltage (Vb), operates so that, for each member Vb,i in a sequence of bias voltage values, it:

• sets the bias voltage value Vb,i on the STJ using the digital-to-analog converter;
• causes a set of values of FI to be captured;
• averages the values of FI to obtain their mean <FI>i;
• computes the standard deviation σFIi of the set of FI values about <FI>i;
• and
• stores the values of Vb and σFI to produce the noise curve.

The apparatus of claim 27 wherein the control logic in the DXP that measures the standard deviation (σFI)i of captured values of FI as a function of bias voltage (Vb,i), operates so that, for each member Vb,i in a sequence of bias voltage values, it:

• sets the bias voltage value Vb,i on the STJ using the digital-to-analog converter;
• causes a set of values of FI to be captured;
• averages the values of FI to obtain their mean <FI>i;
• computes the standard deviation σFIi of the set of FI values about <FI>i;
• and
• stores the values of Vb,i and σFIi to produce the noise curve.

A method of determining locations of Fiske modes as a function of bias voltage of a superconducting tunnel junction (STJ) detector, the method comprising:

• attaching to the STJ a preamplifier that can adjust the STJ's bias voltage Vb by means of a digital-to-analog converter;
• attaching to the preamplifier a digital x-ray processor (DXP) that receives the preamplifier's output and can transmit data to the digital-to-analog converter;
• providing processing logic in the DXP that, on command, can capture a digitized value FI of the preamplifier's output Id;
• and
• providing control logic in the DXP that measures the standard deviation (σFI) of captured values of FI as a function of bias voltage (Vb);
• and
• identifying peaks in a plot of σFI versus Vb (the “noise curve”) as the locations of the Fiske modes.

Apparatus for determining locations of Fiske modes as a function of bias voltage of a superconducting tunnel junction (STJ) detector, the apparatus comprising:

• a preamplifier, for connection to the STJ, that can adjust the STJ's bias voltage Vb by means of an associated digital-to-analog converter;
• a digital x-ray processor (DXP), connected to the preamplifier, that receives the preamplifier's output and can transmit data to its associated digital-to-analog converter;
• processing logic in the DXP that, on command, can capture a digitized value FI of the preamplifier's output Id;
• control logic in the DXP that:
• measures the standard deviation (σFI) of captured values of FI as a function of bias voltage (Vb);
• and
• generates a plot of σFI versus Vb (the “noise curve”) wherein peaks in the noise curve locate the Fiske modes.