Drive and measurement circuit for a photomultiplier
AssigneeET Enterprises Limited
InventorAnthony George Wright
Life of this patent
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Abstract
A method of measuring an anode current in an electron-multiplier device having an anode, a cathode, dynodes and a voltage divider network for applying voltages to the dynodes, which method includes applying an HV positive voltage to the anode and intermediate voltages to the dynodes, the cathode being at or near circuit ground potential, conducting dynode currents through or in parallel to the voltage divider to a point substantially at cathode potential, and deriving from those currents a current representative of the anode current.
Claims17
A method of measuring an anode current in an electron multiplier device having a cathode at or near circuit ground potential, an anode at a relatively high positive potential, a series of discrete dynodes at successive intermediate potentials, and a voltage divider comprising a string of transistors connecting the dynodes to respective points in a resistor string of the voltage divider, the method comprising:
- passing at least some of the dynode currents successively through the string of transistors;
- summing currents flowing in the dynodes and optionally also a cathode current, and deriving the measured current from the summed currents;
- and
- subtracting from the summed dynode currents a standing current in the voltage divider to measure substantially at ground potential a current representative of the anode current and derived from current flowing in the dynodes, without taking a measurement of a current between the anode and the dynode adjacent to the anode.
A biasing and measurement circuit for an electron multiplier having a cathode, an anode and a series of discrete dynodes therebetween, the circuit comprising a maintainer to maintain the cathode at or near circuit ground potential, a connector to connect the anode to a relatively high positive potential, a voltage divider comprising a string of transistors connecting the dynodes to respective points in a resistor string of the voltage divider to apply graduated intermediate voltages to the dynodes, and a measurer to measure substantially at ground potential a current representative of the anode current and derived from currents flowing in the dynodes, without taking a measurement of a current between the anode and the dynode adjacent to the anode;
- wherein the measurer is configured to sum the currents flowing in all of the dynodes and optionally also a cathode current;
- and
- the measurer comprises a subtractor to subtract from the summed dynode currents a standing current flowing in an active arm of the voltage divider.
An electron multiplier comprising a biasing and measurement circuit having a cathode, an anode and a series of discrete dynodes therebetween, the circuit comprising a maintainer to maintain the cathode at or near circuit ground potential, a connector to connect the anode to a relatively high positive potential, a voltage divider comprising a string of transistors connecting the dynodes to respective points in a resistor string of the voltage divider to apply graduated intermediate voltages to the dynodes, and a measurer to measure substantially at ground potential a current representative of the anode current and derived from currents flowing in the dynodes, without taking a measurement of a current between the anode and the dynode adjacent to the anode;
- wherein the measurer is configured to sum the currents flowing in all of the dynodes and optionally also a cathode current;
- and
- the measurer comprises a subtractor to subtract from the summed dynode currents a standing current flowing in an active arm of the voltage divider.
A biasing and measurement circuit for an electron multiplier having a cathode, an anode and a series of discrete dynodes therebetween, the circuit comprising means for maintaining the cathode at or near circuit ground potential, means for connecting the anode to a relatively high positive potential, a voltage divider comprising a string of transistors connecting the dynodes to respective points in a resistor string of the voltage divider for applying graduated intermediate voltages to the dynodes, and means for measuring substantially at ground potential a current representative of the anode current and derived from currents flowing in the dynodes, without taking a measurement of a current between the anode and the dynode adjacent to the anode;
- wherein the measuring means is configured to sum the currents flowing in all of the dynodes and optionally also a cathode current;
- and
- the measuring comprises a subtractor to subtract from the summed dynode currents a standing current flowing in an active arm of the voltage divider.
Dependencies are inferred from the claim text.