Infrared Bakeout Package

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Our new VB series bakeout packages are an easy way to remove water vapor from vacuum chambers. The UHV-compatible IRB-600 short wave infrared radiation emitter mounts on a standard 2.75”/70mm CF flange. The BC-3 controller uses thermocouple feedback to regulate the vacuum chamber temperature, controls the power to the IRB-600 emitter, and sets the total bakeout time. These are all the features that you would expect with a vacuum bakeout package.

What sets the VB series BC-3 apart from other bakeout controllers is the Vacuum Interlock feature. The Vacuum Interlock uses a Setpoint relay on your vacuum gauge controller to regulate the vacuum level in the chamber. For example, if your chamber has ion pumps, you can set your vacuum gauge controller Setpoint to 4 x 10-6 Torr which will turn off the heat to the chamber when the vacuum setpoint is reached.  Whether your chamber has ion pumps or a turbo pump, the Vacuum Interlock feature can be used to ensure that your pump does not get choked with water vapor.

The BC-3 controller can drive two IRB-600 emitters, two heater tapes, or even one of each!

BC-3-Bake-Out-Controller
BC-3-Bake-Out-Controller

Infrared radiation(IR) heats the chamber from the inside out and is very effective compared to external radiant bakeout heaters. The thermal conductivity of stainless steel at 100° C is only 15 W/m K compared to 300 W/m K for copper at 100° C. Therefore, it takes a long time for external bakeout heaters to heat up the inside of the vacuum chamber surfaces. 

IR heats the internal surfaces of the vacuum chamber very quickly. Using internal IR heat even for a short time during the initial pump-down can have a noticeable effect on pumpdown times and base vacuum. To reach low UHV vacuum levels you need to bake for longer periods of time.

IRB-600 emitter
IRB-600 emitter

The short wave IR energy of the IRB-600 emitter drops off as a function of distance. The internal chamber surfaces that are closer to the emitter will become hotter than surfaces that are further away from the emitter. This effect is not precisely linear, but you do need to consider it with regards to thermocouple sensor placement on the chamber. Typically, the thermocouple sensor should be about 6-to-10 inches away from the IR-600 emitter. If you have two IRB-600 emitters on your chamber, place the thermocouple sensor at the midway point between the two emitters.

Once the thermocouple sensor has been placed, you can program the bakeout temperature setpoint. Typically, the bakeout temperature setpoint is programed 20° C-to-30° C lower than the temperature on the surfaces that are nearer to the IRB-600 emitter. If you would like the chamber to be 150° C near the IRB-600 emitter, program the bakeout temperature to 125° C. 

Before using the Vacuum Interlock feature, you need to program your vacuum gauge setpoint to the desired value. Typically, the vacuum setpoint is 3 or 4 x10-6 Torr for ion pumps and 5 x 10-4 Torr for turbo pumps. Then, simply turn the Vacuum Interlock switch on the BC-3 controller to On. If you would prefer to bake the chamber into the turbo pump before you turn on your vacuum gauge, then set the vacuum interlock switch to Off; the IRB-600 emitters will turn on and be regulated only by the vacuum chamber temperature.

In our shop we have a few vacuum chambers that come up to air practically every day, and some days more than once per day. We use the BC-3 with a single IRB-600 emitter and one 600 watt heating tape to effectively remove water vapor. If we know that we will be venting again later in the day, we turn on the BC-3 as soon as we start pumping down the chamber in order to take advantage of viscous flow and to let the turbo pump down the chamber for about 30 minutes. Then we turn off the BC-3 and start the ion pumps; the vacuum chamber will be down in the low 10-8 Torr range within a few hours. If we need a better vacuum, then we bake the chamber out for 8-to-10 hours over night. The following day the vacuum chamber will be in the 10-10 Torr range after the chamber cools down and also using a titanium sublimation pump. Not needing to remove cables and preamplifiers from the chamber is a big time-saver. We use the VB bakeout package practically every day and every time we do, we really appreciate how easy it is to bakeout a vacuum chamber with the BC-3 and IRB-600 compared to external heaters and bakeout blankets.

The BC-3 and IRB-600 are available in 120 VAC and 230 VAC configurations.

For more information on the VB series bakeout controller, visit our website at this link –

https://rbdinstruments.com/products/vb.html

No-bakeout-blankets-required
No-bakeout-blankets-required

11-065 High Voltage Arcing problem and solution and SPX-314 opto-coupler replacement

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As the 11-065s get older we are starting to see instances where the beam voltage, condenser voltage or objective voltage becomes unstable as the front panel potentiometers are adjusted.

The front panel potentiometers can become “noisy” as a result of oxidation on the internal contacts.  In addition to causing instability in the output voltages, it is also possible for the potentiometer output potentiometer “open” up.  When this happens, the output of the beam, condenser or objective supply can go as high as 6.4kV as shown in the picture below in which a 1000:1 high voltage probe is used to measure the beam voltage supply.

In the case of the condenser or objective supplies becoming unstable the result is that the ion beam might go in and out of focus, or the ion beam can get completely shut off.  However, if the beam voltage becomes unstable and goes up to 6.5kV then the opto-couplers on the HV1 board will become damaged and then the emission or pressure circuits will no longer function properly.  The original opto-couplers are only rated up to 5kV.

If you suspect that your 11-065 beam, condenser or objective supplies are unstable, here is how to test the HV1 board outputs;

  1. Turn off the 11-065 and unplug the input power cord.
  2. Place the 11-065 on the bench and remove the top cover
  3. Remove the HV cover (on the right hand side of the unit)
  4. Unplug all of the spade connectors which connect the various wires to the HV1 and HV2 boardsHV1 outputs
  5. Lift out the HV2 board (the one closer to the center of the unit)
  6. Place all of the wires off to the side of the 11-065, making sure that none of them touch the chassis. Most of the wires are outputs and so have no voltage on them, but the 4 center wires on the HV2 board have 20VAC on them.
  7. Connect a high voltage probe to the beam output connector on the still plugged in HV1 board, (the board closest to the chassis) ground reference is the chassis. The outputs are:   E93 Beam Voltage, E90 OBJ, E89 COND.Beam voltage HV1 board
  8. Plug in the 11-065 input power cord.
  9. Make sure that the Beam voltage switch is OFF and the beam voltage knob is turned fully CCW.
  10. Turn on the 11-065 power.
  11. Turn on the beam voltage and monitor the output on the DVM that is connected to the high voltage probe.
  12. Slowly turn the Beam voltage potentiometer CW and observe the DVM reading. The Beam voltage output should increase smoothly from near zero to 5kV as you turn up the potentiometer.  If you see jumping, instability, or if the Beam voltage output goes up to 6.5 kV then the potentiometer is noisy and needs to be replaced.  The potentiometer is a 10 k ohm 5 turn 2 Watt 1% potentiometer available from DIgikey, Mouser and Newark.  
  13. The OBJ and COND outputs go from 50% to 100% of the Beam Voltage.  So to test those, the Beam voltage needs to stay fully CW at 5.0   The OBJ and COND potentiometers are also 10 k ohm 5 turn 2 watt 1% potentiometers. 

If the Beam voltage potentiometer was noisy and the voltage went higher than 5kV, then the opto-couplers were likely damaged.   If your do not get any emission current, then most likely U6 on the HV2 board was damaged and should be replaced.  Other components may be damaged as well. If the emission works but not the pressure, U7 is likely damaged.

On the really old 11-065s, U6 was a TIL109 opto.  When that part became obsolete about 20 years ago, it was replaced with a SPX314 opto.  Most of the 11-065s in the field have been updated to the SPX314 (a modification is required).   If you have a really old 11-065 with the TIL109 opto-couplers, RBD still has a few of those in stock.

Recently, the SPX314 has become obsolete and is hard to find.  It can be replaced with a OPI1264 opto-coupler which is also has 15kV peak of isolation, so even if the HV1 board goes up to 6.4kV this opto-coupler will not get damaged. The OPI1264 will not only repair the problem, it will ensure that this particular problem does not happen again.

There is no modification required to switch from a SPX314 to an OPI1264, but the pin outs are slightly different and are shown in the pictures below.

SPX314 on HV2 board
U6 schematic HV2 board

The long leg on the OPI1264 is pin 1. You need to bend the legs on the OPI1264 so that the pins go into the correct holes on the board. The top hole in the board is pin 1, then it goes pins 2, 3 and 4 with 4 being the bottom pin.

The OPI1264 opto-couplers are available from most major electronic part suppliers including Mouser.

If you need technical help to repair your 11-065 ion gun control you can contact RBD Instruments Inc. for assistance. We offer technical support, repair/ calibration and the use of a loaner 11-065 while your unit is being repaired.

11-010 Electron Gun Control modification to reduce noise

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Due to aging components, many of the PHI 11-010 5kV electron gun controls have developed a slight noise problem in the emission chopper circuit on the 623 board that results in about 300 mV of 60 hz ripple on the emission voltage, which translates into noise in the electron beam and Auger data.

Since the chopper circuit is never used (it was designed as a way to get N/E data with a lock-in recorder), a very simple solution to the problem is to bypass the chopper circuit.

Procedure:

  1. Unplug the 11-010 AC power cord and remove the cover.
  2. Solder a jumper between Pins 17 and 18 on the 623 board as shown below.  The 623 board is located on the side of the 11-010, just above the filament supply board.

This modification will reduce the noise level from about 300 mV to 50 mv or less and results in noticeably cleaner Auger data.

Chopper board resistors
This jumper will bypass the Chopper board circuitry
Chopper board schematic
Jumper location on Chopper board