Transcript cern2016cast61-part2x

Status of the InGrid detector
for 2016
Christoph Krieger
The InGrid detector for 2016
Main features:
• Ultrathin silicon nitride window
• Drift cylinder with field cage
• Readout module hosting 7 InGrids
(central chip surrounded by 6 chips to
veto partial tracks mimicking X-rays)
• Decoupling of grid signal
• Two veto scintillators
(a small & a bigger one)
Ultrathin silicon nitride windows
First batch of silicon nitride windows made by Norcada:
• 14 mm aperture with 3x3 array of membranes
• 200 nm membranes plus 20 nm Aluminum
• 0.5 mm ribs with 200 µm thickness
• 5 windows delivered to Bonn end of last week
• Also received 2 “rib devices“ of 500 µm thickness for
reinforcing window structure
Testing at Bonn:
• Will (re)setup improvised vacuum teststand
used for samples end of last year
• Glue windows onto new cathode plates &
SLOWLY pump them
• Foresee destructive pressure test for at
least 1 or 2 windows as well as several
pumping & venting cycles
• Will glue “rib device” to 2 windows
• Feedback to Norcada as soon as possible
for second batch
Readout module hosting 7 InGrids
• Central chip surrounded by 6 “veto” chips
• Track fragments mimicking low energy X-ray events
can be vetoed as rest of track is visible on “veto” chips
• Should contribute most to the background reduction at low energies
Status of “The Magnificent Seven” readout module:
• New electronic boards (intermediate board & chip
carrier) have been received and are being assembled
• Mechanic parts have been submitted to workshop
(already 2 months ago, still waiting…)
• Testing of electronic parts is starting right now
• About 20 InGrids from batch IZM-7 are available for
the 2016 InGrid detector
Drift cylinder with field cage
• Outer chips are quite close to drift cylinder
• Inhomogeneous electric field expected in this region
• Equipped existing drift cylinder with simple field shaping
structure to minimize distortions
• Copper strips on Kapton with SMD resistor chain
Decoupling of grid signal & veto scintillators
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Decoupling of induced grid signal is foreseen
Ortec preamplifier will be used as close to detector as possible
Signal will be sampled with an FADC
Signal shape will help to discriminate tracks perpendicular to chip surface mimicking ~ 8 keV photons
Small piggyback veto scintillator on backside of detector for same reason
Bigger veto scintillator on top of shielding to veto fluorescence X-ray photons induced by cosmic rays
Time between last veto signal and FADC trigger is recorded
Veto scintillators can only be used together with decoupling & sampling of grid signal
None of these is expected to significantly improve low energy background (depends on trigger threshold of
FADC and noise)
• Veto scintillators shall be read out with SiPM, currently some issues with electronics to read out SiPMs, still
to be understood
• Further tests on decoupling the grid signal start next week (has already worked before)
Readout system & software
• New features have been implemented in readout firmware but need testing with
hardware (only available now)
• Readout of seven chips already working, may need a bit of timing adjustment for
new hardware
• Interplay of FADC trigger and readout of chip already implemented in firm- &
software, already mostly tested
• Operation of HV power supply now integrated in readout software, uses same
bus as FADC readout, already mostly tested (need to check with long USB)
• Reminder: frame-based, untriggered readout of chip
• FADC trigger will close frame after short delay, else frame is closed after defined
time, all frames are read out & recorded, timestamp of FADC trigger is recorded
• Time between last veto scintillator signals and FADC trigger is recorded
• Still a lot testing & debugging to do
Preparation of the infrastructure @ CAST
• InGrid’s vacuum system remounted at the end
of April and brought back to life
• Afterwards last opportunity of laser alignment
was used
• IMPORTANT: chameleon installed ;)
• Needle valve will have to be exchanged for
operation with ultrathin windows
(Pressure gradient ~< few mbar/min required)
Measuring InGrid’s position
• After laser alignment InGrid’s position
was remeasured by the geometers
• Same measurement was done last
November before dismounting
• Position is calculated by measuring points
on three circumferences & fitting circles to the points
(stated precision is ~ 1 mm)
• Old & new position agree with in few 100 µm in X and within 1 mm in
Y & Z, taking into account measurement precision it seems to be fine
• Alignment precision of ~ 0.5 mm expected from laser alignment
(included in systematic uncertainties in chameleon analysis)
Installation end of July
• Foreseen to start in week 30 (25.7)
• Rough schedule:
25.7 Arriving at CERN with the equipment/detector
26.7 Installing the additional infrastructure for the detector & modify the vacuum
system for really slow pumping
27.7 Setup the detector (not mounting it yet) and get it running & perform a dry
run for the slow pumping (no thin window) & start
pumping XRT
28.7-28.7 Debug the detector & keep pumping XRT
1.8-2.8 Mount the detector & last debugging of detector plus tests
3.8 Really slow pumping of InGrid vacuum with thin window in place
4.8 Pumping until desired pressures are reached
5.8 Mount shielding
• If possible, shifting by one or two weeks would help with tight schedule and allow for a
bit more testing at Bonn, should not affect start of the run… possible???
Status of XRT vacuum system
• Currently there is no one responsible for operation & maintenance of
XRT vacuum system
• Bonn cannot do it, neither enough manpower nor enough money
• Who will be responsible for operation & maintenance of the XRT
vacuum system in 2016 and beyond?
• In April sudden pressure rise in bellow region caused system to stop,
reason unknown but maybe hinting at failing turbopump
• Spare(s) for turbopumps available, but pump types no longer serviced
by Leybold  if spares are used up, we are screwed
The InGrid detector beyond 2016
• Just some ideas… (on request of Wolfgang)
• Even thinner window: 100 nm silicon nitride
• Maybe Timepix3-InGrids (datadriven readout, similultaneous
measurement of time & charge, …)
• Adopt design of current SRMM (copper body)
• Depends on funding!
Conclusion, Outlook & Questions
• Building the 2016 InGrid detector: thinner windows & more chips
• Very tight schedule: still a lot of things to test & debug
• Testing of first full-size ultrathin 200 nm windows will start this week
• Installation foreseen for end of July
• Maybe shift schedule by one or two weeks to gain time for more
testing at Bonn??? (should not affect start of the run)
• Who will be responsible for operation & maintenance of the XRT
vacuum system in 2016 and beyond?
• Who has to approve the operation of the XRT with the ultrathin
windows before opening the XRT downstream gatevalve?