Transcript People

Latest results of MICE amplifier
testing
Andrew Moss
Daresbury Laboratory
August 2013
People
Over the last couple of months a intensive period
of RF testing and power supply optimisation by
the following people has brought good results,
thanks too:• Kevin Ronald, Colin Whyte, Alex Dick –
Strathclyde Uni
• Chris White, Tim Stanley, Steve Griffiths –
STFC
• Saad Alasri – Imperial/STFC
Andrew Moss
Test system at Daresbury
Andrew Moss
Status of Amplifier s and power supplies
• In June 2012 using an old ISIS test tube we reached 1MW RF output
power.
• New tubes were then put in the 4616 tetrode and 116 Triode amplifier
cavities so that we could push towards 2MW demonstration.
• However many power supply issues developed which limited our ability to
sustain high voltage for periods of time, and by October 2012 we could not
generate more than 300kW without crowbarring of the HV power supply
• When we removed the new MICE tube from the amplifier cavity, it was
clear that issues were occurring in the HV tank, the valve was burnt on its
HV input contact
• To speed up testing parts of the HT input of CERN amplifier were used on
the LBNL amplifier cavity – causing incorrect location of the valve in the
socket. Thankfully this damage is light and not a problem
Andrew Moss
Original LBNL design,
water in , steam out
CERN design has two water
pipes, MICE must do the
same – to speed this up we
used some CERN parts
This lead to a dimension
change here and aloud the
tube to sit too far down in
the socket – resulting in
finger strips sitting on
painted area of triode tube,
hence anode was not
correctly connected
to the
Andrew Moss
supply
Restart of testing
• During November 12 to January 13 new parts were manufactured to
remove the incorrect valve seating issue and the amplifier rebuilt with the
old ISIS tube again
• Testing restarted however the limit of 300kW and power supply
crowbarring was still present
• Power supply testing revealed that the crowbar device itself was at fault
and this was replaced with an old thyratron with a limited capability – max
30kV and 1/10th the current handle capability we needed, it would do but
was at risk of being destroyed if a fault occurred
• This allowed us to go back to RF testing with the old ISIS tube and we
were able to get back to 1MW RF output power – the gain of the old tube
was limiting us at 9dB – 200kW drive = 1MW output
Andrew Moss
Temporary crowbar solution
• Colin Whyte had been negotiating with e2v
over a replacement full spec crowbar, and
was offered 3 prototype versions, condition
unknown, for us to try as a fast non
guaranteed solution rather than 6 months for
a new crowbar
• With prototype number one fitted (June
2013) we were able to standoff 38kV DC
with reliable crowbar operation in test
conditions without the RF amplifier in
circuit
• With the MICE Triode valve refitted to the
amplifier circuit we were in a position to
attempt to pass the previous high power
record of 1.2MW
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Going for power
•
•
•
Continuous measurement of X-ray
and Microwave radiation was
performed during high power
operation – only background levels
for in both cases
Steady improvements in power
numbers started to appear over the
following weeks, however there were
still problems with crowbarring and
low gain
Mark Keelan from ISIS alerted us to
an adjustment we had not previous
tried to use – ¼ wavelength tuning
stub on the HT line – this should be
adjusted to minimise RF going back
towards the power supply and firing
the crowbar
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2MW
• Several attempts at tuning the HV
quarter wavelength stub were
made and in combination with
adjusting the RF pulse structure
we were able to minimise RF sent
back inside the power supply
• This is properly the key to
stopping the problem crowbar
events
• Immediately we were able to run
at 35kV and –
• Continued to run at this level for a
good period of time and preform
other measurement's
• Multiple runs at this power level
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RF Parameters
• Tetrode 18kV 15 amps 217kW drive
• Triode 35kV 130 amps = 4.5MW electrical
power
• Electrical conversion efficiency – 48%
• Gain – 10.3dB
• Output power – 2.06MW
• Very pleased with results and system looks
stable at maximum power
Andrew Moss
Andrew Moss
Andrew Moss
The Next step
• Tiara milestone needs to be achieved, this requires the
amplifier system to be operated in the MICE hall
• Amplifiers and power supplies are currently being striped out
of test area ready for transport to RAL on 19th Aug
• Program of work to rebuild system is understood but is very
high work load
• Components being delivered from Don Summers Mississippi –
coax and test loads so that system can be run at a maximum of
1MW
• In fact a huge amount of equipment is in transport to Don and
then to RAL
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Andrew Moss
Summary
• Many electrical problems over the past year have
been resolved
• Crowbar device is temporary and needs a solution in
the future for the MICE experiment – possibly a solid
state device – tests will be done
• 2MW RF power has been achieved with amplifier
system after many years of work, lots of experienced
gained and new RF people now on hand to dedicate
their time
• Amplifier system will be installed in experimental
hall in the near future and operate
Andrew Moss