New high speed 5kV floating Picoammeter

RBD Instruments has released a new version of its 9103 USB Picoammeter which incorporates faster reads per second with 5000 DC volts of isolation to chassis ground.

9103 HV

9103 HV

 

 

 

 

 

 

 

 

Increasing the DC voltage isolation from chassis ground to 5000 volts (5kV) opens up new possibilities for researchers such as direct DC current measurement of very small electron and photo multiplier signals.  Electron and ion beam measurements can be biased to reduce secondary electrons or to retard the beam as needed for experiments.

Designed to provide accurate bipolar DC current measurements in noisy environments such as synchrotron beam lines, the 9103 can measure bi-polar DC currents from low picoamps to milliamps.

The drawing below shows how the 9103 is floated on your HV power supply.  The high voltage is referenced to chassis ground, and the signal ground is referenced to the high voltage.   To help keep the supply and signal connections clear, the HV connection is a MHV connector and the signal input is a SHV connector.

Floating picoammeter

Floating picoammeter

 

There are a number of manufacturers of programmable DC power supplies that can be used to float the 9103 up to whatever voltage is needed (as long as you do not exceed +/- 5 kV).

For example, TDK-Lambda provides a programmable 0 to 6.5kV supply that can be voltage limited to 5 kV and can drive up to 2 mA of current.

The model number for a 120 VAC line input is PHV6.5P2-USB-1P115.  The base model has a ripple of 700mV which is somewhat high, but TDK-Lambda does offer a low ripple option that gets the ripple down to 75mV.  You can also easily make a simple RC filter to do the same thing.    A number of interface options are available (USB, Ethernet, Serial, analog….

TDK Lambda supply

TDK Lambda supply

 

 

 

 

PHV series

PHV series

 

 

 

 

 

 

 

 

The new high speed option for the 9103 increases the reads per second from 40 to over 500, which is fast enough to perform optical chopper experiments.  And, by taking more reads in the same amount of time as the first generation 9103 could, the accuracy is improved.

The Actuel software included with the 9103 provides new features for high speed acquisitions and display, but you can also write your own software to control the 9103 using the simple ASCII commands or in LabVIEW.

Since 9103s can be synced, it is now possible to configure a multichannel DC Picoammeter with up to 256 channels that has high speed, high voltage, or both options.

And if you do not need the high speed or high voltage options, the standard 9103 USB Picoammeter is still available as well.

For more information visit the RBD Instruments website at http://www.rbdinstruments.com

 

04-500 Old style X-ray source filament conversion

The very early PHI 04-500 and 04-548 X-ray sources used a small filament that had couplers to make the connection between the X-ray source and the filament.

04-500 04-548 old style filament

04-500 04-548 old style filament

 

 

 

 

 

 

 

 

 

In addition, the couplers were held in place with a notched ceramic that had a special pointed set screw which pressed into a copper wire that in turn made the connection to the electrical feedthrough on the source.

 

 

 

 

 

 

 

 

 

This connection scheme worked well enough as long as you set the filaments properly and did not ramp the current up too quickly.  Even then, the filaments were prone to warping out of shape over time.  Also the couplers could loosen up and then the filaments would short out.

PHI’s solution was to redesign the filament where the filaments were brazed into a ceramic base instead of using couplers.  This resulted in a very stable filament base where the filaments can’t move at all and so they no longer warped out of position (unless you ran the filament current up too quickly).

Recently I updated an older 04-500 X-ray source from the old style to the new style filaments.  You can see the before and after in the pictures below.

old 04-500

Old Style 04-500 X-ray source

new 04-500

Updated 04-500 X-ray source

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This update will result in more stable X-ray source operation and extended filament lifetime.

The new style filaments cost more than the old style filaments by quite a bit.  But factoring in the improved performance, longer lifetime and reduced downtime it may be worth the additional cost.

If you have an old style source please keep this filament conversion in mind the next time you need filaments or a complete source rebuild.

Contact RBD Instruments for more information.

Hydraulic quick coupling seal replacement

The Hydraulic Quick Couplings (quick connect) used on PHI X-ray sources are Parker type SH2-62.

These couplers are used to connect the heat exchanger to the X-ray source in order to keep the anode from overheating.  Over time the seals in the female coupler can fail from wear or simply drying out.  When that happens you will get a steady drip of water from the coupler (not good as if water leaks into the source it will arc) .

This post will explain how to find and replace the seals in the female coupler.  The male coupler is non serviceable (but also usually does not fail). Some pictures of the fitting and seals are at the bottom of this post.

There are two parts to the seal mechanism.

  1. A Teflon seal retainer
  2. A Nitrile O-ring seal

Parker fitting cut away

You can find these parts at any Parker distributor (Google Parker quick coupling) or by searching for the part numbers.

The Teflon seal retainer is PN MS28774-015

The Nitrile O-ring is PN 2-015 N1470-70

If you search for the part numbers you will find lots of places that carry these parts.  They are very inexpensive.  In fact, the next time you order parts from RBD for your PHI X-ray source just ask and we will throw some in with your order at no charge.

Once you have the parts, here is how you install them:

  1. Use a dental pick and dig out the Teflon spacer and O-ring
  2. Install the new O-ring. You can use the dental pick to guide it into the channel. Note that the O-ring needs to be towards the bottom of the coupler
  3. Install the new Teflon spacer using the dental pick to guide it into the channel. Note that it needs to be installed towards the top of the coupler. Also, for the Teflon spacers that I purchased for this blog post, they have a slit in them which is probably supposed to make it easier to install.  However, I think it would have been easier with a solid spacer like the old one I pulled out.  It was a little bit tricky but by using a screw driver I was able to flatten the slit so that it finally snapped down into the channel.  You should plan on losing one or two of the Teflon spacers as you refine you technique.

Finally, here is a link to a the Parker Hydraulic Quick connect catalog – 3800-B_Hydraulic.

 

male and female couplers

male and female couplers

Coupler with leaky seals

Coupler with leaky seals

Dental tool to remove old spacer and seal

old spacer and seal

old spacer and seal

Screwdriver and dental tool

Screwdriver and dental tool

Coupler with new seals

Coupler with new seals