Cable and equipment shielding

I've been trying to learn more about shielding equipment and cables. I've bought some books and read some archived posts but haven't found anything like what I'm trying to do.

I have an analog sensor with a sampling rate of 1-2MHz and 12-14bit. The cable we use has an overall shield and each of the twisted pairs are also shielded. I am getting what I assume is EM interference. When the system is used near a magnetron at 6-15MeV we get a very small but annoying amount of noise. About 150mV positive only spikes.

We have simulated the noise using a TIG welder's high voltage arc start feature. When not welding, just letting the torch point straight up we get a HUGE amount of noise, much more than we get near the magnetron. What ever type of noise this is, it can be picked up by an ionization chamber quite well. Our only choice is to use this source of interference as a test of our equipment before we travel to the customer's site. When we touch the source of the HV, turning our bodies into antennas I guess, the sensor quits working completely. In fact, a motion control system in the next room crashed and started free running into its hard stops!

From what I understand the power is supplied to the magnetrons via a coaxial at 10,000v 1000-10,000A in extremely short bursts at a maximum of 200-250 pulses per second. There are then transformers which step that up and finally something magic happens in the magnetron and we get 6-15MeV.

The high voltage pulse cables (10,000v) are extremely well shielded. They are running in the same cable tray with some unrelated BNC cables (for about 110 feet) and with a 5vp-p signal there is no interference. That leads me to think that the interference is coming from the destination. We can only modify our equipment, so I am looking into what it will take to shield it from everything possible.

My biggest question is what to do with the cable shield. Which end do we connect it to? I've read in the past that you should connect the shield to the end where you care about the signal MOST. Other people suggested you connect the shield on the opposite end of where you care about the signal. Should it be connected on both ends?

Thanks : )

Grant

connect the sensor cable shield to the sensor at the sensor end and connect the cable shield to your test equipment at the test equiment end but.... isolate the sensor and cable grounds from the other system.

keep your sensor and test system electrically isolated from the other system except AT ONE PLACE only. This will usually be at the 3rd prong of the power cord.

You want your system to have its own totally enclosed shield that doesn't connect to the other system except at one place only.

This will eliminate ground loops.

If your sensor and cables are all well shielded and you eliminate the ground loops and you still have a problem then we have to dig further.

If your sensor MUST be electrically connected directly to the other equipment for some logistics reason, then the problem becomes MUCH more difficult.

Mark