Calibration procedure of MKS Baratron 722A

PHYS3710 Short Experimental Project I (Radiometer) MKS Baratron 722A calibration procedure manual A. Introduction o To calibrate the MKS Baratron 722A using vacuum system o Learn the proper operation procedures of vacuum pumps (Rotary vane mechanical pump and diffusion pump) B. Operation procedures o Connect the MKS Baratron 722A to the vacuum system. o Understand the various components of the vacuum system Vent Valve Main Valve
Rough Valve
Oil Trap Liquid N2 Inlet Pirani Gauge Forepump Valve Oil Mist Filter Revision v1.0 Page 1 of 3 PHYS3710 Short Experimental Project I (Radiometer)  The rotary vane mechanical pump can evacuate the chamber to ~10‐2 Torr. It acts as a forepump for the diffusion pump and rough pump for the chamber.  The diffusion pump can evacuate the chamber to 10‐4 Torr. It can ONLY operate at pressure lower than 10‐1 Torr, otherwise the oil is spoiled!  Oil trap condense the diffusion pump oil and reduce contamination to the chamber. Liquid nitrogen is the coolant for the oil trap, it also traps water vapor.  The Pirani gauge can display pressure between 2000 to 1 microns (1 mmHg = 1000 microns)  The cold cathode gauge can ONLY be turned on at pressure below 10‐3 Torr. It can can display pressure ranged 10‐3 ~ 10‐8 Torr. Main Valve Pirani Gauge controller and Display controller o
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Revision v1.0 Turn on the rotary pump  Open rough valve, CHECK the Pirani gauge pressure is decreasing  When the Pirani gauge pressure is below 100 microns, close the rough valve and open the forepump valve  Wait until the pressure is below 100 microns Turn on the diffusion pump  [Cautions!] Make sure the diffusion pump heater is turned on with running cooling water and Pirani gauge pressure is below 100 microns Page 2 of 3 PHYS3710 Short Experimental Project I (Radiometer)  Allow the diffusion pump to warm up, wait for 10 mins  Add Liquid nitrogen to the oil trap.  [Cautions!] Wear liquid nitrogen protection groves. o Pumping down the MKS Baratron gauge 722A  Close the forepump valve and open the rough valve  When the Pirani gauge pressure is below 100 microns, close the rough valve and open the forepump valve  Open the main valve o Calibrate the MKS Baratron gauge 722A  When the Pirani gauge pressure is below 20 microns,  Turn on the MKS I‐Mag Cold cathode gauge controller.  Switch to H.V. ON, pressure reading should show up on the display.  Pressure is displayed in AA x 10BB Torr format  Turn on the MKS Baratron gauge 722A  The full scale reading of the MKS Baratron gauge 722A is 1 Torr  The voltage output range is 0.000 to 10.000 V  Allow the pressure to decrease below 1.0X10‐3 Torr  Set the voltage to the corresponding pressure reading by adjusting the ZERO port using a small screwdriver. C. Troubleshooting o Please contact Technician / TA for assistance. D. Shutting down o On the MKS I‐Mag Cold cathode gauge controller, switch to H.V. off and then turn off the controller. o Turn off the MKS Baratron gauge 722A. o Close the main valve. o Turn off the diffusion pump, allow the pump to cool down (~20 mins). o After the diffusion pump has cooled down, turn off the cooling water, close the forepump valve and turn off mechanical pump. o Open the Rough valve and then open the Vent valve GENTENLY. o You may disconnect the MKS Baratron gauge 722A and connect it to the Radiometer experiment apparatus. o Close the Rough valve and the Vent valve. o Restore the equipment status upon project completion. Prepared by Gary Lai Date: 20/08/2014 Revision v1.0 Page 3 of 3

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