Automating Hydrogen Gas Flow for the DECY-13 MeV Cyclotron

During my internship at PSTA-BATAN, I developed an automated control and monitoring system for the DECY-13 MeV cyclotron's hydrogen gas flow using LabVIEW and National Instruments (cRIO-9025).

Objective

The DECY-13 MeV cyclotron at the National Nuclear Energy Agency of Indonesia (PSTA-BATAN) requires a precise hydrogen gas flow to act as its ion source. During my internship, I designed and deployed an automated control system to regulate this flow, replacing manual valve adjustments and significantly reducing the risk of human error.

System Architecture

The system bridges high-precision physical valves with real-time digital control using a National Instruments (NI) hardware stack and a LabVIEW graphical interface.

Main Controller: NI CompactRIO-9025 acting as the central embedded controller.
Actuation (Analog Output): An NI 9381 module supplies the control voltage ( $V_v$ ) to a Pfeiffer Vacuum EVR 116 motorized gas regulating valve.
Acquisition (Analog Input): An NI 9201 module reads the output voltage ( $V_f$ ) from an Aalborg GFM Mass Flow Meter.
Connectivity: An NI 9923 terminal block connects the NI 9381 pins to the physical system.

LabVIEW Software Design

The LabVIEW program acts as the central software interface. It takes the operator's desired flow rate in Standard Cubic Centimeters per Minute (sccm) and translates it into the corresponding valve control voltage.

Safety Interlocks

To prevent gas over-pressurization within the cyclotron, I engineered a safety threshold into the LabVIEW Block Diagram. If the system detects a flow rate exceeding the upper operational limit of 10 sccm, the program automatically triggers an emergency stop—setting the valve output to $0V$ and halting the gas flow.

Calibration and Data Modeling

A critical phase of the project was calibrating the digital inputs and outputs against the physical flow characteristics. I conducted multi-day empirical tests across various initial tank pressures (45 to 70 psi) and analyzed the behavior using LibreOffice Calc.

Sensor Calibration (Linear)

The relationship between the actual flow $F$ (in sccm) and the flow meter's voltage output $V_f$ proved highly linear with an $R^2$ of 0.99. The derived calibration equation used in the LabVIEW block is:

MATH.TELEMETRY // EQ.02LATEX.KATEX

F = 10.2 \times V_f - 0.1

Valve Actuation (Exponential)

The relationship between the applied valve voltage $V_v$ and the resulting gas flow was non-linear. Regression testing confirmed that an exponential function provided the most accurate fit with an $R^2$ of 0.96:

MATH.TELEMETRY // EQ.04LATEX.KATEX

F = 1.5 \times 10^{-4} e^{4.5 V_v}

When linearized for the LabVIEW control logic, the required voltage for a target flow becomes:

MATH.TELEMETRY // EQ.06LATEX.KATEX

V_v = \frac{\ln(F) + 8.8}{4.5}

Conclusion

The deployed NI-based control system successfully automated the DECY-13 MeV cyclotron's hydrogen delivery. By translating theoretical calibrations into LabVIEW real-time logic, the project delivered a reliable, safe, and precise gas flow environment for subsequent particle physics experiments at BATAN.