Detecting tiny pulses after a very large one

The beam in the LHC is supposed to have gaps in it that allow the ejection kickers time to rise to their proper values. If there is residual beam in these gaps, the kicker would sweep it through the volume of the nearby superconducting magnets which might cause them to quench.

As far as I know, that didn't actually occur yet, but the beam intensity in the LHC is raised ever higher in the interest of getting more physics results out of this very expensive machine. With increasing intensities come increasing losses. A way to measure the magnitude of the problem is the first step towards solving it. That, at least, is my understanding.

Well, this beam is already around 26GeV, and kickers are hefty objects at those energies. Before adding lots of expensive hardware, let's see if we can solve the problem by properly adjusting the beam handling RF.

Jeroen Belleman

Ahh! Thanks! Yeah we did this flux gate thing with saturation... I couldn't understand it till I made this silly model and wrote down the inductor voltage as V-sub-L = L di/dt + i dL/dt. (OK not sure about the signs....)

OK silly idea, George H.

Why, pray tell?

Jeroen Belleman

These are in common usage in the accelerator community. You are welcome to propose better ones. If they are really good, we may even adopt them. But no one will listen to a bad-tempered s.e.d. denizen having nothing better to contribute than the simple declaration that they are 'brain dead metaphors'.

Jeroen Belleman

Recently saw an ad from Aeroflex/Metelix for some surface-mount RF power limiter things. Some can handle hundred-watt RF pulses at GHz, and guarantee no more than 20 dBm out, something like that.

That could be a good start at the front end. Attenuate your monster signal down to where these limiters can handle it, and you're halfway done.

Thanks, John. I'll check them out.

Regards, Jeroen Belleman

Here they are:

This has schematics:

That in a nutshell is one of the basic pulse radar problems. Considering the power levels you should look towards short range capable heavy radar for typical schemes. Something like SPS-48 or SPS-51 radars might use.

?-)

The Pin diodes used in the Iridium Sat Phone LNA switch chip could switch between more orders of magnitude in power levels between the Tx signal and the Rx signal in < 10ns with signals up to 5GHz into 50 Ohm loads.

Impedance matching would be required for the current transformer to stripline

Yes, except that the radar guys usually deal with comparatively narrow bandwidths, which allows using tricks with lambda/4 transmission lines. I can't do that here.

Jeroen Belleman

Considering

radar

use.

Yes there is a lot of that, but that is not all of the tricks. They also did noise blanker type tricks.

?-)

You do presumably know the timing, so you could actively drive a PIN diode attenuator, and maybe some downstream analog gates.