Transcript Charge Measurements on VELA

Charge Measurements on VELA
Alex Brynes
BPM (stripline)
ICT
FCUP
WCM
In Practice
• Signals from all devices are fed
into here – we need to interpret
these and convert them into pC,
shot-to-shot.
• We don’t want to have to take
cables in and out, twiddle knobs
etc. – this can, and should (?) be
done remotely.
• Prototype system working –
needs many improvements.
• WCM / FCUPs – only the first peak of the signal ( x conversion factor ) is needed.
• ICT – the entire area under the curve – a bit more tricky.
Hardware Controllers
•
In order to make the interface
to hardware more userfriendly, controllers for
various VELA components
were written.
• Currently have: scope, BPM,
magnets, RF, screens,
shutters, vac valves, cameras.
• See guide for more info:
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notes\VELA_Hardware_Controlle
rs_Guide_v1.docx
Type
Function
void
monitorTracesForNShots
void
monitorNumsForNShots
std::vector<std::vector<double>>
getScopeTrace
std::vector< double >
getMinOfTraces
std::vector< double >
getMaxOfTraces
std::vector< double >
getAreaUnderTraces
std::vector< double >
getAvgNoise
double
getScopeP1-4
double
getWCMQ/ICTQ/FCUPQ/EDFCUPQ
std::vector< std::string >
getScopeNames
Scope
•
•
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Currently less than ideal –
scope traces are written to
EPICS via this console and
then interpreted using a
hardware controller.
This depends on a Python
script which is prone to
crashing.
We can’t write all four full
scope traces to EPICS at
10Hz this way – this was
sufficient last year but may
not be enough for 100Hz
operation
Also depends on scope
setup, especially for ICT.
• Ideally, Diagnostics / Controls should do this – this may be the case in future but we
will have to rely on this for now!
BPMs
•
•
•
•
If we can correctly interpret
the voltage induced on the
four BPM pickups for a given
resistance (attenuation), we
can calculate the current,
and thus the charge.
To get the charge, we need
to know: the four voltages,
two attenuations ( + two
delays ), and a “calibrated”
charge value ( BPMs are
most accurate in a given
charge range ).
Then to calculate charge for
each shot.
BPM hardware controller
does all this – prototype
working as of last year.
See
http://projects.astec.ac.uk/EBTFManual/index.php/Catego
ry:Charge_Measurements#Using_BPMs
http://projects.astec.ac.uk/EBTFManual/index.php/Diagno
stics:BPMs
Screens
• Given a gain, and a known charge reading, the pixel intensity on a
screen can be calibrated and then used as another diagnostic.
• Not absolute, but still useful.
• Needs more work before this can be used routinely.
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ion\notes\VELA Wall Current Monitor Charge Measurement
Monitoring in EPICS.docx
Examples
• BPM-to-charge GUI (also plots WCM / ICT /
FCUP)
• RF auto-crest (prototype)
• BPM re-calibrator
• VELA status monitor
Plans for next run
• SP1 Fcup should be the most accurate, and so
should be used to calibrate all other devices.
• All new BPMs, ICTs, etc. need calibrating –
better procedure for ICTs.
• Sort out scope interface with help from
Controls/Diagnostics.
• Controller interface to multiplexer.
• Discuss scope setups for planned experiments.
Software Improvements
• Everything is a prototype at the minute, lots of
improvements are needed to current
software.
• Operators should try these out, suggest
improvements.
• Also try writing software using the hardware
controllers – charge should be monitored for
most experiments.
Desired Software
• Auto-setting of charge using laser – if we are
ever allowed to control laser.
• Robust calibration procedure.
• Beam intensity on screen -> charge.
• Suggestions?