a. baldini psi 18 july 2007 meg overview cobra (w. ootani) lxe calorimeter (s. mihara) calibrations...

A. Baldini PSI 18 July 2007

MEG Overview

• Cobra (W. Ootani)

• LXe calorimeter (S. Mihara)

• Calibrations (G. Signorelli)

• Drift Chambers (J. Egger)

• Timing counter (F. Gatti)

• Electronics and DAQ (M. Grassi)

• Software (R. Sawada)

• Schedule

• The shielding and grounding scheme was improved after the December run.

• There hasn’t been no unexpected shutdown since then.

• No shutdown for ~10 days with SC+NC+Bypass during shutdown period.

• No shutdown for ~10 days with SC + (BTS) after accelerator started to run.

• The problem by the external noise seems fixed.

Quench Problem Status (W. Ootani)

A new problem happened during CW accelerator testing.

COBRA was unexpectedly shutdown after 40 hrs operation.Still under investigation, but it seems there was a problem with NC power supply according to the measured waveform.

Xenon detector (S. Mihara)Xenon detector (S. Mihara)Honeycomb panel test completedHoneycomb panel test completed

• 3rd panel delivered to Pisa at 16:30 on 20/Feb

• Mounted on the text box and tested on 22, 23/Feb– 3 bar– Inspection by a Plyform expert– 4 bar x4 times

• Hold for 3 minutes at 4 bar in the last test

– Panel deformation (max) • 0.3 mm at 1 bar• 3.4 mm at 4 bar

Holes for evacuation

Cryogenic Test at SIMICCryogenic Test at SIMIC

• -18/May– All nuts on the covers of the cold vessel were fas

tened tightly and the warm vessel was evacuated whole weekend.

• 21/May– He leak test. 1.8Bar He was filled and found that

the leak rate was larger than 10-4 mbarl/sec. Keep evacuation during the night.

• 22/May– cooling using cold gas from the LN2 tank. Cold g

as in the cold vessel Most parts were cooled down to -5~-10 degree C.

• 23/May– liquid N2 through the cooling pipe. All parts coole

d below -110 degreeC around 12:00.– Then N2 gas at 1.0Bar and He gas filled step by

step with measuring leak rate.• N2 1.0 bar He 0.2 bar 5x10-7 mbarl/sec• N2 1.0 bar He 0.4 bar 1.6x10-6mbarl/sec• N2 1.0 bar He 0.6 bar 7.8x10-6mbarl/sec• N2 1.0 bar He 0.8 bar 2.2x10-5mbarl/sec

• The leak was not fixed at SIMIC by any means.

• We decided to bring the cryostat to PSI and perform a leak test

Cryostat arrived at PSICryostat arrived at PSI

• Delivery at 7:00 am on 5/June

• Works to be doneCleaningLeak/pressure testAlignment– PMT installation– …

CW received on middle of mayCW received on middle of may(G. Signorelli)(G. Signorelli)

LED

PMT Gain

Higher V with light att.

Can be repeated frequently

alpha

PMT QE & Att. L

Cold GXe

LXe

Laser

Laser

(rough) relative timing calib.

< 2~3 nsec

Nickel Generator 9 MeV Nickel γ-line

NaI

Polyethylene

0.25 cm Nickel plate

3 cm 20 cm

quelle

onoff

Illuminate Xe from the back

Source (Cf) transferred by comp air on/off

Proton Acc Li(p,)Be

LiF target at COBRA center

17.6MeV

~daily calib.

Can be used also for initial setup

KBi

TlF

Li(p, 0) at 17.6 MeV

Li(p, 1) at 14.6 MeV

radiative decay

0 - + p 0 + n

0 (55MeV, 83MeV)

- + p + n (129MeV)

10 days to scan all volume precisely

(faster scan possible with less points)

LH2 target

e+

e-

ee

Lower beam intensity < 107

Is necessary to reduce pile-ups

Better t, makes it possible to take data with higher beam intensity

A few days ~ 1 week to get enough statistics

XenonCalibration

DC (J. Egger)

4 Levels of test

1. Pretest HV Air + tightness

2. Aquarium : functionality + tightness

3. Cosmics Lab : other preamps + correct signal assignment inside COBRA up to panel

4. Cosmics E5, with and without COBRA

DC test with Cosmic ray (in Lab.)

cosmic ray counter for DC wire alignment

• 10 counters (10 plastic scintillators + 20 PMTs) are prepared

• DC wire alignment will be performed w/o COBRA field

TC: F. Gatti

TC: MC vs data: E loss in bars

6 years of operation !!

Positron efficiency

Confirmed by a 3° calculation including PR, tracking and fitting from DC to TC

Trigger installation

Positrons from “off-centre” -decays and

hitting DCH outer frame

missing hits

missing hits


Where do they come from?

x (cm)

y (c

m)

Front view (x-y) of

-decay vertices on

the target

all events

2>50 || N1<5

Source of inefficiency

for the TC


Way(s) out?

• Reduction of beam spot size on the target? (x,y 1.1 cm 0.5 cm)

– is it achievable by shrinking the target (not this year)– Background ? Investigate...

Increase of the magnetic field?– shrinking of the bending radius by 1 cm needed increase of B by 7% (B0 = 1.26 T 1.35 T)

distortion of hit pattern on TC? might it affect COBRA behaviour?

• ...


Multi-threading model

VMETransferThread

CalibrationThread

CalibrationThread

CalibrationThread

CalibrationThread

CollectorThread

VME

Round-Robindistribution

Network

Zero-copy ring

buffers

Zero-copy ring

buffers

Electronics and DAQ: M. Grassi


DRS Readout rateOptimal readout rate of DRS full waveforms with 4

calibration threads: 30 events/sDuring Dec 06 run max readout at 7 events/s

– Double event readout– Code optimization– Single calibration thread


DAQ rate vs. amount of data

• DAQ speed is not a limiting factor• The total data size needs solution:

– 30 Hz is maximal VME speed for full waveforms → >270 MB/sec

– Data transmission limit is 20 MB/sec (=250TB/year)→ need online reduction 10x (M. Grassi’s and R. Sawada’s talk)

– Storage limit is 30 TB/year→ need offline reduction 8x (R. Sawada’s talk)


Conclusions • Splitters: installed, operational, expected performances, test

in Dec 06• Fiber preamp: problem with an IC fixed, test passed,

mounted on the TC detector, installation in Aug 07 • Hit registers: mezzanine boards produced, FPGA firmware

ready (PSI GPVME board), installation in Aug 07 • Trigger: installed, operational, built-in debugging and control

tool, need tuning after detector turn on, test in Dec 06• DRS2: installed, operational, good for timing, temperature

dependence, usable with DC• DRS3: prototype test phase, final solution, not available in

2007• Aux digitizer: production problem solved, prototype test

completed successfully, ready for 2007 run • DAQ: installed, operational, good performances, test in Dec

06 run

The electronics and the DAQ systems are expected to be ready for the 2007 run


Software (R. Sawada)


Pdf’s – 1)

ee++ SignalSignal

RDRD

AccidentalAccidental

SignalSignalRDRD

AccidentalAccidental

All pdfs normalized to 1All pdfs normalized to 1 and and summed by relative weightssummed by relative weights of different types of events. of different types of events.Positron FWHMPositron FWHM improved from improved from 1.0 1.0 0.8 %; 0.8 %; photon FWHMphoton FWHM improved from improved from 6.5 6.5 5 %. 5 %.

FWHM = 0.8 %FWHM = 0.8 %

FWHM = 5 %FWHM = 5 %


Pdf’s - 2)

tt

Signal + RD

Accidental (assumed flat)Accidental (assumed flat)

Signal

Accidental (assumed flat in cos Accidental (assumed flat in cos ))

RDRD

tt assumed assumed flat for accidentalflat for accidental and and gaussian for signal/RDgaussian for signal/RD (MC results predict gaussian (MC results predict gaussian shape, but with worse resolution); shape, but with worse resolution); taken from MC taken from MC (results close to the proposal FWHM). (results close to the proposal FWHM).

FWHM = 180 psFWHM = 180 ps FWHM FWHM 1 1oo


Sensitivity result

Three different sets of Three different sets of windows: windows: results do not results do not depend on the cutsdepend on the cuts. .

The sensitivity limit isThe sensitivity limit is 2.15 x 102.15 x 10-13-13

equivalent to equivalent to the the sensitivity that one sensitivity that one obtains with a boxobtains with a box

analysis assuming analysis assuming 0 0 bckbck. .

(not surprising). (not surprising). Important point: Important point: the spill-the spill-

inin of bck events within the of bck events within the

signal region is signal region is automaticallyautomatically

taken into account by taken into account by thethe

knowledge of the bck knowledge of the bck pdfpdf..

2.15 x 102.15 x 10-13-13

of “null” experiment of “null” experiment N.B. Empty circles & crosses shiftedby 0.05 on B.R. axis for clarity.


Advantage: boundary effect

Box analysisBox analysiswindowwindow

Likelihood analysis windowLikelihood analysis window

0 events in 0 events in box analysisbox analysis

Box analysisBox analysiswindowwindow

Likelihood analysis windowLikelihood analysis window

1 event in 1 event in box analysisbox analysis

Box analysisBox analysis: : quote a worse upper limit, with a “sudden jump”. quote a worse upper limit, with a “sudden jump”. Likelihood analysisLikelihood analysis: treated as : treated as a bck fluctuationa bck fluctuation, likelihood value only , likelihood value only slightly changed slightly changed upper limit increases by a small amountupper limit increases by a small amount andand continuouslycontinuously..

MEG status report

32PSI: February 14th 2007PSI: February 14th 2007PSI: February 14th 2007

Conclusions

First result: very good agreement of rates predicted by MC no significant

unwanted backgrounds !!


Schedule

a. baldini psi 18 july 2007 meg overview cobra (w. ootani) lxe calorimeter (s. mihara) calibrations...

Documents

bar 5x10

cold gas

cold vessel

n2 gas

mayhe leak test

cobra center17

shutdown period

unexpected shutdown