Electrical contact to individual electrodes is accomplished by inserting the pins of a 0.100 inch (2.56 mm) pitch header into holes in the tabs extending through the housing. A picture of this connection is shown in the left image of Fig. 4.3. The potential on the source electrode (Esource) is controlled by a Spellman SL10 high voltage power supply (Spellman High Voltage, NY, USA).
Ion injection into the drift region is facilitated by the application of a floated high voltage pulse to the injection mesh/electrode. The high and low levels of the pulse are controlled by a homebuilt high voltage power supply, connected to a GHTS 60 A push-pull switching unit (Behlke, MA, USA). Timing of the injection pulses was controlled by a DG535 digital delay/pulse generator (Stanford Research Systems, Inc., CA, USA). The voltage gradient within the drift region of the IMS is supplied by connecting electrodes to different probe points along a resistor chain constructed from 1.0 MX precision resistors (TE Connectivity, PA, USA). The voltage at each end along the resistor chain (VdriftHIGH and VdriftLOW in Fig. 4.1) is controlled by a homebuilt high voltage power supply. The resistor chain and high voltage lines are housed in a 3D printed PLA/PHA housing with MHV connections for input voltages. The entire drift tube assembly, with associated electronics is shown in the left image of Fig. 4.3.
The Faraday plate at the terminus of the drift region is connected to a Keithley 428 current amplifier (Keithley Instruments, OH, USA) and the inverting output is recorded on Tektronix TDS 2024C 4-channel oscilloscope (Tektronix, OR, USA). Signal acquisition on the oscilloscope is triggered on the injection pulse.
Operational Parameters of 3D Printed IMS
Control of the IMS makes use of 5 different voltage inputs and timed square wave pulses for ion injection. In each experiment performed with the 3D printed IMS, potentials applied to the emitter (Vspray), focusing electrode (Vfocus), first drift ring (VdriftHIGH), and final drift ring (VdriftLOW) were 4500, 2500, 2000, and 300 V, respectively. During ion injection pulses the voltage on the injection electrode was either 50 or 100 V, relative to VdriftHIGH. At all other times the voltage of this electrode was -25 V, relative to VdriftHigh (Vblock). For all experiments, ions were gated into the drift tube at a repetition rate of 10 Hz.