Re: Muon-On-Request

[Michael Barnes <barnes@triumf.ca>]

Dear Peter,

Thank you for the note. I read through the note and have the following 
main comments and questions:
d_switch is probably more like 250ns, rather than the original 200ns. 
The majority of the ~250ns delay (~170ns) is attributable to the fiber 
optics, MOSFET driver and MOSFET. The 170ns has increased slightly 
(~15ns), since the original design, mainly due to for the inclusion of 
the two parallel 6.2R resistors on the gate of the MOSFETs. In addition, 
to reduce "overlap" of the FET stacks, during switching, the turn-on 
delay (with respect to turn-off) in the controls has been increased to 
approximately 63ns. If deemed necessary we can recover 18ns of the 
increase in the controls delay by modifying a setting on the controls 
card. However, this will increase "overlap" current in the stacks, 
during switching, and therefore increase power dissipation in both 
resistors and MOSFET cards -- so I would prefer not to do this.

On the plus side, the TRIUMF TTL splitter box has a considerably shorter 
delay than the original (Boston) splitter box: I can't recall the actual 
numbers, which are in a logbook at TRIUMF [I'm on sabbatical at CERN], 
but believe that the TRIUMF splitter has a delay of less than 20ns 
compared with 60ns to 80ns delay, I believe, for the Boston splitter.

Am I correct in interpreting  your note that the average frequency is 
29kHz for the kicker in Muon-On-Request mode? (compared with 
approximately 37kHz for the present operating mode).

Peter Winter can confirm the overall delay through the TRIUMF TTL 
splitter  box, controls, etc to the pulse rise.  To do this I would 
recommend the following measurement  procedure:
1) Use 2 high impedance (e.g. x10) probes and deskew them both (to have 
the same timing) at the input to the TRIUMF TTL splitter box;
2) Use one of these high impedance probes as a trigger for the scope, 
connect the other probe directly on the output of one of the capacitive 
pick-ups on the beam tank (by directly I mean WITHOUT Anatoly's box --- 
this box includes an "integrator" and delay cable so would distort the 
timing measurement);
3) Note the delay between the rise of the TTL signal and the rise of the 
deflector plate voltage.

NOTE: we have deliberately set-up the timing of HV1 & HV2 to be 9ns 
delayed with respect to the timing of  MV1 & MV2: this is to allow for 
the beam propagation delay from the input of plates MV1 & MV2 to the 
input of plates HV1 & HV2. The 9ns delay also ensures that the beam 
"sees" the same pulse width at both sets of deflector plates. You should 
be able to see this 9ns delay depending on which end of the beam pipe 
you make the timing measurement at. The 9ns delay is achieved by adding 
9ns worth of 50R coaxial cables to the inputs of cabinets HV1 & HV2.

Best regards,
Mike

Peter Kammel wrote:

>>*Please remind me what operating conditions you would ideally like for the Muon-On-Request mode. Thanks.*
>>
>>    
>>
>Dear Mike, dear Gary,
>
>Sorry, it took a day to think a bit more carefully about the
>muon-on-request scheme. Attached is a little note on this issue.
>As far as I can tell (but others will check for loopholes) it looks
>really promising.
>
>Best regards
>
>Peter
>