Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 53

High-stability high-voltage power supply for MRTOF†
P. Schury,∗1 M. Wada,∗1 H. Wollnik,∗1,∗2 J. -Y. Moon,∗1,∗3 T. Hashimoto,∗1,∗3 and M. Rosenbusch∗11
Allan deviation [ppm]

Achieving the highest possible mass resolving power
in a multi-reflection time-of-flight (MRTOF) mass
spectrograph requires very high-stability power supplies. To this end, we have developed a programmablehigh-voltage power supply that can achieve long-term
stability on the order of parts-per-million. We havedemonstrated that in the ≤1 Hz band the output stability is on the level of 1 part per million (ppm) during one hour, with only slightly more output variation
across 3 days. We have further demonstrated that theoutput is largely free of noise in the 1 Hz–200 Hz band.
We have also demonstrated settling to the ppm levelwithin one minute following a 100 V step transition.
Finally, we have demonstrated that when these power
supplies are used to bias the electrodes of an MRTOF
the measured time-of-flight is stable on the ppm-level
for at least one hour.
In order to achieve a fast-settling, high-precision,
long-term stable high-voltage power supply for driving our MRTOF, we have extended the concept laidout in the Voltage Multipliers, Inc, application note
“AN-0300 - High Voltage Op-Amp Application Using
Opto-Couplers,1) ” which describes the use of infrared
LEDs and high-voltage photodiodes to emulate an operational amplifier with up to 15 kV power supply span.
A conceptual circuit diagram of our design, separated
into functional blocks, is given in Fig. 1.
A crate of 16 power supplies was built to bias the20-bit DAC

16-bit digital
thermometer
5.000 V

5.000 V

5.000 V

5.000 V+--+5 kV

D1Filter

U4R LED

Q2+50 kΩ49.95 MΩRgRfCfb

D2

D4-5 kV-Precision resistive divider

Q1

10 nF++15 V

D3

1MΩ

R'gR'fLow-noise reference

VoutVset

Gain adjustment+-15 VRegulation circuit with"high-voltage op-amp"

∗1
∗2
∗30.1

1

10Cluster time [s]100

1,000Fig. 2. Allan deviation from individual ion times-of-flight.
The PID regulation without and with RC filter exhibit
a slope approximating white noise to ≈1 s and ≈10 s, respectively. The dashed line indicates the trend expected
for white noise. The Allan deviation curve switches
to a flat line indicative of flicker noise at a level of≈0.02 ppm, which coincides with the 0.1 ns raw bin
width from the TDC.

electrodes of 50 cm MRTOF-MS in the E3 (KISS)
vault. The voltages were adjusted until a time resolvt≈ 250,000 was achieved. Due to theing power of ∆tlens voltage requiring a bias of 5 kV or more, we havethus far opted to use an NHR 42 60r high-precision±6 kV power supply from ISEG to bias this electrode.
Figure 2 shows the result of an analysis of timeof-flight data from a several-hours-long measurement
using our newly developed power supplies with theMRTOF in E3 along with a similar analysis using
pre-existing hours-long duration data from our fullsize MRTOF-MS operated with a PID stabilization
scheme. The data for the PID stabilization was obtained using a 30 ms cycle period, yielding a minimum
Allan deviation2) sampling period of ≈80 ms. The datafor the present system was obtained using a 15 ms cycle
period, yielding a minimum Allan deviation sampling
period of ≈40 ms. These analyses shows that in termsof long-term stability the voltage stabilization circuitof the present work exceeds the performance of our RC
filter enhanced PID regulation system. Using our newpower supplies, the MRTOF exhibits white noise in
the ion time-of-flight over a much wider duration thanwith the PID-based regulation systems.
References

1) “AN-0300 - High Voltage Op-Amp Application Using
Opto-Couplers,” Voltage Multipliers, Inc, http://www.
voltagemultipliers.com/pdf/High-Voltage-Op-Ampand-Linear-Regulator-App-Notes.pdf .
2) N. El-Sheimy, H. Y. Hou, X. J. Niu, IEEE Trans. Instrum. Meas. 57, 140–149 (2008).

Fig. 1. Design of the high-voltage stabilization circuit.
†PID w/o RC Þlter
PID w/ RC Þlter
Present work

0.01

Digital controls
MCU

0.1

Condensed from Rev. Sci. Instrum. 91, 014702 (2020)
KEK Wako Nuclear Science Center
New Mexico State University
Institute for Basic Science- 126 -