Malte HildebrandtMEG Review Meeting, 18.02.2009 Malte Hildebrandt MEG Review Meeting Feb 2009 Drift...

Malte Hildebrandt

MEG Review Meeting, 18.02.2009

Malte Hildebrandt MEG Review MeetingFeb 2009

Drift Chamber System• hardware status Run 2008• shutdown activities 2009

Malte Hildebrandt


Outline

• installation 2008

• MEG Run 2008: • characteristics of HV instabilities

• tests with dc system in MEG

• tests in laboratory

• Shutdown • preparations, tests

• first test results

• Summary / Outlook

Malte Hildebrandt


Installation 2008

• main changes / improvements in 2008 compared to installation in 2007: → topics were already noted in last years DC Status Talk at the Review Meeting

as „needs to be done“ / „ will be improved“)

• improved strain-relief of LV and signal cables at inside patch panel

→ no disconnected LV cable 2007: LV dc6u disconnected

→ 13 missing signal channels 2007: 42 missing connections ↔ crucial step during installation:

closing end-cap

• more detailed analysis of optical survey of dc system

→ geometrical alignment includesslope of wires along z-axis

2007: wire at constant x and y, parallel to z-axis (UCI group startet to implement slope)

Malte Hildebrandt


Installation 2008



• optimised target

→ new support spacers and 2007: target slightly misalignednew attachment screw-plate to correct position in space

→ slant angle adjusted to (20.5 ± 0.3)° 2007: (12.8 ± 0.5)°

Malte Hildebrandt


Target

2007 2008

Malte Hildebrandt


Installation 2008






→ identification marks on target

Malte Hildebrandt


Installation 2008






→ identification marks on target

→ measurements of inclination:

• conventional (sliding rule) 2007(2008): conventional

• photogrammetric 2007: photogrammetric • optical survey

Malte Hildebrandt


New DC HV Modules

• during Run 2008: modification of dc HV modules

• observation (in 2007, June - July 2008):

• several times “blocking” / “freezing” of complete communication: MSCB Submaster, HV nodes, LabView

• in combination with HV trips of several HV modules

but: cause and effect not clear…

→ new HV modules: • watchdog: reboot of Controller in case of

missing toggle signal from Controller (→ HV off)

• new bus driver: „state machine“ decouples from the bus when not transmitting data → no blocking of bus

line with „active high signal“ in case Controller stucks

• smaller capacitance at HV_output reduces trip propagation within HV module

• geographical addressing of nodes within crates

↔ S.Ritt↔ R.Schmidt

Malte Hildebrandt


HV Performance

• summary: • many dc planes / modules suffered from frequent HV trips

• consequently theses planes / modules could only be operated with reduced HV settings

→ huge impact on overall performance of dc system(→ talk by B.Molzon)

Malte Hildebrandt


HV Performance

• summary: • many dc planes / modules suffered from frequent HV trips


→ huge impact on overall performance of dc system(→ talk by B.Molzon)

• phase 1: June – July • 30 / 32 planes >1800 V (remark: nominal 1850 V)

beam • 2 planes showed problems right from beginning

• phase 2: Aug • dc system most of the time off, short period on beam

• 19 / 32 planes >1800 V• 6 / 32 planes 1700-1800 V

• phase 3: Sep – Dec • further deterioration of HV performance beam

• 11 / 32 planes >1800 V • 7 / 32 planes 1700-1800 V

Malte Hildebrandt


Phase 1

• phase 1: June – July

• beam, start-up phase, e.g. HV ramping

• 2 dc planes showed problems right from beginning• dc10A: always <1300-1500 V• dc03A: once 1850 V, then setback down to 1300 V,

recovery within weeks up to 1700 V

• all other planes: air admixture to COBRA gas (outside module) necessary to achieve stable dc operation

→ cHelium ≈ 95-96 % (reading O2 sensors)

(instead of „pure“ helium level around 99.0-99.5 %)

Malte Hildebrandt


Air Admixture

Tue, 01.07., 08:45 55ccm / 2000ccm(2.75 %)

Sun, 06.07., 23:00 40ccm / 2000ccm(2.00 %)

cHelium=95 %

cHelium=99 %

Sat, 12.07., 15:00 32ccm / 2000ccm(1.60 %)

Mon, 30.06., 08:15 30ccm / 2000ccm(1.5 %)

Mon, 30.06., 17:4565ccm / 2000ccm(3.25 %)

cHe= ~93 %

~94-95 %

~95-96 %

Sat, 19.07., 02:00 32ccm / 2000ccm(1.60 %)

Wed, 16.07., 12:40 24ccm / 2000ccm(1.20 %)

~96-97 %

~95-96 %

Malte Hildebrandt


Phase 1

• phase 1: June – July

• beam, start-up phase, e.g. HV ramping

• 2 dc planes showed problems right from beginning• dc10A: always <1300-1500 V• dc03A: once 1850 V, then setback down to 1300 V,

recovery within weeks up to 1700 V

• all other planes: air admixture to COBRA gas (outside module) necessary to achieve stable dc operation

→ cHelium ≈ 95-96 % (reading O2 sensors)

(instead of „pure“ helium level around 99.0-99.5 %)

→ end of July: 30 / 32 planes operational with >1800 V (remark: nominal 1850 V)

• occasional problems with communication of HV modules / MSCB / LabView

→ modify HV modules during XEC run

Malte Hildebrandt


Phase 2

• phase 2: August

• beam, XEC run, Dalitz run

• XEC run: • dc gas system running continuously

• dc HV system off for 2 ½ weeks (modifications of HV modules)

• 10 days dc HV at 800-1000 V

• Dalitz run (e+ e- identification in Dalitz decay 0 → e+ e- )

• 5 days dc HV on nominal values→ current load / plane: 0.7-1.0 A

(compared to 10-12 A with beam)

• but: many HV trips, number of „weak“ planes increased

→ beginning of September: • 19 / 32 planes >1800 V• 6 / 32 planes 1700-1800 V

Malte Hildebrandt


Phase 3

• phase 3: September – December

• beam: MEG physics run

• several tests with running system: • to understand reason of HV trips→ see separate transparency • to possibly stop or even

recover deterioration

• but still: many HV trips, number of „weak“ planes increased further

→ end of December: • 11 / 32 planes >1800 V• 7 / 32 planes 1700-1800 V

• in parallel: new test setup in laboratory (HV pcb, potting of capacitors, HV)→ see separate transparency

Malte Hildebrandt


HV Trips

• characteristics of HV trips:

• individual „treshold effect“ for affected planes

• deterioration due to frequent trips (due to damage ?)

• no obvious correlation with beam off / on, magnetic field off / on or muon target / CW target tube

↔ exception for 2-3 planes: • beginning of run period: HV trip while beam blocker opened→ improved during run time („training“ ?)

• during run period:HV trip 10-20 min after beam blocker closed

Malte Hildebrandt


HV Trips


• beginning of run period: air admixture to COBRA gas necessary to achieve stable dc operation→ cHelium ≈ 95-96 %

• significant deterioration started after:

• beam time (XEC, Dalitz)

• 2-3 months with dc + COBRA gas and HV

→ at beginning: same planes affected as in 2007

• further deterioration due to frequent HV trips during remaining run time (2008: May – Dec)even without any further beam time

• stable operation (with reduced HV settings)during second beam time (5 days)

2007: cHelium ≈ 96 %

2007: at end of run

2007: after 2-3 monthswith gas and HV

2007: similar, but:shorter run time(Sep – Dec)

2007: dc system offduring beam time

Malte Hildebrandt


HV Trips









2007: cHelium ≈ 96 %

2007: at end of run




→ deterioration due to beam time ?

Malte Hildebrandt


HV Trips









2007: cHelium ≈ 96 %

2007: at end of run




→ deterioration due to beam time ?

→ deterioration due to helium environment ?

Malte Hildebrandt


Tests during MEG Run

• infrastructure / hardware: • independent Bertan HV power supplies

• HV cables

• trip test with oscilloscope (MEG and lab)→ no improvement

• variation of dp_dc regulation value (pdc-pCOBRA): • ↔ small leaks ?

Malte Hildebrandt


Location of HV Problems

• HV problems at top of U-branches: systematics or just by chance ?

level of dp_dc measurement

• dc operation at slightly lower dp_dc

• dc operation at slightly higher dp_dc

dp

→ due to difference in ρ of He and He/C2H6:

15th Oct 2008

Malte Hildebrandt


Location of HV Problems

• HV problems at top of U-branches: systematics or just by chance ?

level of dp_dc measurement

• dc operation at slightly lower dp_dc

• dc operation at slightly higher dp_dc

→ due to difference in ρ of He and He/C2H6:

15th Oct 2008

dp

Malte Hildebrandt



• infrastructure / hardware: • independent Bertan HV power supplies

• HV cables

• trip test with oscilloscope (MEG and lab)→ no improvement

• variation of dp_dc regulation value (pdc-pCOBRA): • ↔ small leaks ?

• 0.2 Pa → 2.0 Pa→ -10% current / plane due to breathing of dc modules→ no improvement

• increase ethane fraction in dc counting gas: • ↔ inside sensitive volume ?

• He / C2H6: 50 / 50 → 45 / 55

→ reduction of gas gain by nearly factor 2→ no improvement

Malte Hildebrandt



• increase air admixture to COBRA: • ↔ outside dc module

• phase 1: cHelium ≈ 95-96 %

• cHelium ≈ 95-96 % → ~40 % → 0 %

→ only test that showed effect→ but not that clear result as expected for obvious problem „outside of dc module“

→ summary of tests with dc system during MEG run period:

• no clear cause and effect

• but: hint, that problem is connected to longterm exposure to helium (inside and / or outside of dc module)and - at least in some cases - is located outside of dc module !

→ ensure helium atmosphere during christmas holidays and shutdown→ see separate transparency

Malte Hildebrandt


Tests in Laboratory

• check of common aspects of construction / assemby

• sequence of production and assemby → no hint from logbook

• wire tension → no hint from logbook

• HV pcb

• sealing / potting of capacitors

• sealing / potting of HV soldering spot2007: several times weak point

→ new test setup:

• HV test setup

• pcb, potting material

• helium environment

• T ≈ 40-45° C

• longterm test (>3 months)

Malte Hildebrandt


HV Test Setup in Lab

→ new test setup:

• HV test setup

• pcb, potting material

• helium environment

• T ≈ 40-45° C

• longterm test (>3 months)

Malte Hildebrandt


HV Test Setup in Lab

• 6 test samples: • 2 samples concentrating on sealing of HV cable,no resistors, no capacitors (Fri, Nov 7th)

• 2 samples with HV cable, resistors, capacitors (Fri, Nov 7th, Thu, Nov 13th)

• 1 sample with pcb_left and pcb_right (Thu, Nov 13th)

• 1 sample: pcb glued on Cu-plate (Thu, Nov 20th)

• all tested in air at 2kV

• status test: • cHelium > 99% (reading of three O2 sensors)

• all HVs at 1990V

• T = 40-45° C (since Mon, Nov 24th)

→ update 17.02.2009:• no significant deterioration (still 2kV) → no conclusion for “aquarium” test

(“aquarium” = dc test setup in laboratory during shutdown)

Malte Hildebrandt


2nd Pressure Control System

• construction of 2nd pressure control system for laboratory

→ operate „aquarium“ independentlyfrom MEG pressure control system

reminder: • „aquarium“: • setup to operate two dc modules

with He / C2H6 as counting gas

• within helium atmosphere

Malte Hildebrandt


Helium Cabin

• closed volume (V = 5.7 m3)

• windows / frames removable→ access to dc modules

• operated with the MEG pcs

• helium sensor in exhaust line of helium cabin (instead of dc exhaust line)

• patch panel is interface / accessible → dc system can be operated like

in COBRA

→ ensures helium environment for dc system during „waiting time“ in lab

→ cHelium ≈ 95 % (conditions like in COBRA)

Malte Hildebrandt


Test Tesults

→ first results from dc module tests in laboratory

• weak point: potting of HV soldering spot on pcb

Malte Hildebrandt


HV Connection

anode decoupling capacitorshood readouthood Vernier pattern

pre-amplifier cardsHV connection to pcb + sealing

→ weak point: potting of HV soldering spot on pcb

Malte Hildebrandt


HV Sealing

cable isolation

HV line

dielectricum

potting

braided shield

pcb

→ nominal condition

→ observation after run periodseveral pottings show:

• change of shape („flowed away“)

• change of color (white → brown)

• same observation in 2007/8(badly applied? no!)

Malte Hildebrandt


HV Soldering Spot

Malte Hildebrandt


Test Tesults



→ replace ThreeBond 1530 with epoxy EPO-TEK 302-3M

Malte Hildebrandt


Test Tesults



→ replace ThreeBond 1530 with epoxy EPO-TEK 302-3M

• „circumstantial evidence lawsuit“ (no glow by eye, IR camera, ...):

• signals on oscilloscope: positive anode signals

negative cathode signals

• change of gas mixture: no effect (or long delay)

→ discharge between anode channel and GND

but: not towards cathode strip and not in sensitive volumemaybe towards frame at the edge

or on pcb itself

→ open dc module to verify or falsify: • wires and cathode foil fine• edges of isolators fine→ closer look at vias on pcb

Malte Hildebrandt


HV Via

top layer

bottom layer

+HVGND

7 mm

Malte Hildebrandt


dc01A

no glue glueno glue

Malte Hildebrandt


PCB Cross Section

GND +HV

pcb

+HV

G10 isolator

glue glue glue

G10 isolator

glue

glue

carbon frame

air

He / C2H6

He

pcb

bottom layer

top layer

bottom layer

Malte Hildebrandt


PCB Cross Section

GND +HV

pcb

G10 isolator

glue

+HV

glue glue

G10 isolator

glue

glue

carbon frame

d

pcb

Malte Hildebrandt


PCB Cross Section

GND +HV

pcb

G10 isolator

glue

+HV

glue glue

G10 isolator

glue

glue

carbon frame

pcb

Malte Hildebrandt


Depth of HV Vias dc01A

→ example: depth of HV via on dc01A

upstream downstream

a0 0.73 ± 0.03 0.76

a1 0.47 0.80

a2 0.39 0.66

a3 0.14 0.83

a4 0.65 0.67

a5 0.57 0.46

a6 0.64 0.61

a7 0.00 0.47

a8 0.57 0.57

location of discharge(identified by signals)

remark: all numbers in mm

ddesign = 0.80 ± 0.02

Malte Hildebrandt


PCB Cross Section

GND +HV

pcb

G10 isolator

glue

+HV

glue

G10 isolator

glue

glue

carbon frame

He / C2H6

pcb

Malte Hildebrandt


Next Steps

→ following activities will start immediately and run in parallel: motto: confirm „via hypothesis“, start new construction / repair work to proof solution

• operate „dc skeleton“ (2 anodes + middle cathode) in „aquarium“

→ no hood cathode: observe discharge ?

• prepare new sample for HV test box: • no glue on ring of via

• glue only on ring of via

• fill via completely with glue

→ confirm effect of different „via / glue conditions“

• start construction of anode frames with new pcb design

Malte Hildebrandt


HV Print 2009

HV print 2009

• traces for HV on middle layer

→ no HV traces on bottom layer

→ individual layers with „only HV“ or „only GND“ (3-layer →4-layer pcb)

• „blind vias“

→ vias have only necessary depthto connect appropiate layers(like „blind hole“)

vias for +HV

pads for resistors

+HV traces

outer edgeprint 2007

print 2009

inner edge

GND

Malte Hildebrandt


Next Steps

→ following activities will start immediately and run in parallel: motto: confirm „via hypothesis“, start new construction / repair work to proof solution

• operate „dc skeleton“ (2 anodes + middle cathode) in „aquarium“

→ no hood cathode: observe discharge ?

• prepare new sample for HV test box: • no glue on ring of via

• glue only on ring of via

• fill via completely with glue

→ confirm effect of different „via / glue conditions“

• start construction of anode frames with new pcb design

→ operate 1st and 2nd dc in „aquarium“ to confirm long term behaviour

→ chance to check for additional „hidden“ weak point (masked by „via problem“)

Malte Hildebrandt


Time Schedule

→ following activities will start immediately and run in parallel:motto: confirm „via hypothesis“, start new construction / repair work to proof solution

detector laboratory

February – March • „dc skeleton“ in aquarium• „via test“ with pcb

• test new dc‘s in aquarium

April – July • ongoing test in aquarium

July – August • test of dc system in support structur in laboratory

beginning of September → dc system ready for installation in MEG experiment

detector workshop

• construction of new dc‘s:anodes with new pcbrecycled cathode + hood

• ongoing construction

Malte Hildebrandt


New DC Preamplifier

• goal: • improve signal / noise ratio

→ improve R- and z-resolution for small signals

→ improve efficiency

• argument: • analysis of experimental data 2007 using low-pass digital filter:→ improvement in z-resolution and 10% higher efficiency

• solution: • select low-noise operational amplifier

• adapt schematics

→ bandwidth reduced from 140 MHz to 80 MHz

• status: • few prototypes produced and tested

→ signal / noise ration improved by factor 1.5

• to do: • direct comparison of old and new preamplifier with real signals

→ dc in „aquarium“ with cosmics and 90Sr

Malte Hildebrandt


Summary / Outlook

• many dc planes / modules suffered from frequent HV trips


→ huge impact on overall performance of dc system and MEG experiment

• many tests were performed in MEG experiment and in laboratory in order to understand this problem

including: upgrade and construction of new laboratory infrastructure

• following weak points were identified so far:

• potting of HV soldering spot on pcb → seal with epoxy

• HV via on pcb → anode frames with new pcb design

• ongoing activities: • confirm via hypothesis

• start construction / repair work to proof solution

→ dc system ready for installation at beginning of September

Malte HildebrandtMEG Review Meeting, 18.02.2009 Malte Hildebrandt MEG Review Meeting Feb 2009 Drift...

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