tpc field cage progress report

ALICE-LHCC Review May 14, 2001

Thomas C. Meyer/EP-AIT 1

TPC Field Cage Progress ReportTPC Field Cage Progress ReportTPC Field Cage Progress ReportTPC Field Cage Progress Report

Project ScheduleTechnical Progress &

PrototypingContractual Matters



Field Cage: Project ScheduleField Cage: Project ScheduleField Cage: Project ScheduleField Cage: Project Schedule



Tests & PrototypingTests & PrototypingTests & PrototypingTests & Prototyping

HV– High ionization behavior (83Kr)

Temperature stabilization– Resistor chain cooling

Construction material– Compatibility and leaks

Electrical network– “From strip to central electrode”



High Voltage StabilityHigh Voltage StabilityHigh Voltage StabilityHigh Voltage Stability

History:– Field cage was exposed to >16 x expected

average charged particle intensity in CERES beam (~ 6000/cm2 s).

– Field cage was operated at 1.78 x nominal drift field (~700 V/cm) in pure CO2.

Surface charge phenomena appearing at 60 kV (≥ 400 V/cm).– Insulation gap safe at ≥ 100 kV.



High Intensity High Intensity 8383Kr TestKr TestHigh Intensity High Intensity 8383Kr TestKr Test

Inject 83Kr with 300 MBq total intensity into field cage (May 2001)

Separate tests for drift and insulation volume.



Temperature StabilityTemperature StabilityTemperature StabilityTemperature Stability

History:– Require:T everywhere ≤ 0.1 ºC– Resistor rod produces 60 W waste heat.

– Liquid cooling (H2O) proven very efficient with negligible gradient inside rod but…

H2O unsuitable at HV (dissociation), Inert liquids dangerous in case of leaks.

New approach: Gas cooling



Resistor Rod: Gas CoolingResistor Rod: Gas CoolingResistor Rod: Gas CoolingResistor Rod: Gas Cooling

Unlike liquid cooling, T inside rod always > 0.1 ºC.– --> must insulate rod!

Foam for test Double wall for ALICE.

T [ºC]

z [m]Ambient level2.5



Gas Cooling: ResultsGas Cooling: ResultsGas Cooling: ResultsGas Cooling: Results Inside of rod achieve tmin of 7 ºC

with 20 m3/h of air:Air Temperature along the rod vs. Flow

0

5

10

15

20

25

30

35

40

45

0 2 4 6 8

Temperature [Celsius]

20m 3̂/h 15m 3̂/h 10m 3̂/h 5m 3̂/h

Gas Flow

Tin = 16 ºC

7 ºC



Gas Cooling: ResultsGas Cooling: ResultsGas Cooling: ResultsGas Cooling: Results

Outside of rod achieve required T of ≤ 0.1 ºC within a few cm from rod:

Numbers are given in units of 1/100 ºC;

Blue numbers indicate zone around rod with

T < 0.1 ºC



Material testsMaterial testsMaterial testsMaterial tests

Drying

-250

-200

-150

-100

-50

0

50

-250

-200

-150

-100

-50

0

50

0 100 200 300 400 500

TEMPERATURE STABILIZATION : +/- 0.4 CPRECISION OF MEASUREMENT : +/- 10 μm

L/L

[µ

m/m

]T[ h]

Macrolon

Carbon Fiber

Kevlar Fiber

Glass Fiber

Wet

Leak test of full-size end plate sector with “CERES” gasket

Humidity tests of FC material



Voltage Divider: Central ElectrodeVoltage Divider: Central ElectrodeVoltage Divider: Central ElectrodeVoltage Divider: Central Electrode

Focus on “stretched foil” version High modulus carbon-fiber frames

NA48 Example



Voltage Divider: Rods & StripsVoltage Divider: Rods & StripsVoltage Divider: Rods & StripsVoltage Divider: Rods & Strips

Ongoing prototyping of all rod types– Resistor rod– HV supply rod– Laser rod– Regular support rod

Verification of strip tension and mounting scheme– Vertical or horizontal?



ToolingToolingToolingTooling

Modification of DELPHI support frame– Needed for construction & assembly of FC– Major handling tool for all operations– Finished by end of 2001



Infrastructure: SXL2Infrastructure: SXL2Infrastructure: SXL2Infrastructure: SXL2

Preparation of dedicated clean area for TPC assembly in LHC interaction region 2:– Finished by December 2001

Clean zone in hall SXL2



Contracting: FC CylindersContracting: FC CylindersContracting: FC CylindersContracting: FC Cylinders First „Invitation to Tender“ (IT-2726) was

launched on schedule in 2000, but...– all offers (4) were above funding level.

Changed scope of tender:– Only production of individual parts

(panels & flanges)– Procurement by and assembly at CERN

New tender (IT-2999) sent April 2001– 6 months delay in schedule



Contracting: End PlatesContracting: End PlatesContracting: End PlatesContracting: End Plates

First „Price Inquiry“ was made in 2000.– Lowest bid exceeded funding by large factor.

Try to achieve savings by…– splitting production process

(raw material, welding, machining), and– design changes.

New tenders to be launched this month– only if expected savings materialize!

Overall production delay ≥ 6 months.



Contracts: Consequences for CERNContracts: Consequences for CERNContracts: Consequences for CERNContracts: Consequences for CERN

Higher manpower load on CERN (TA2) Higher risks in terms of…

– technical failure, quality control, liability, warrenty!

– schedule slippage, – capital loss.

We expect to catch up on the baseline schedule during the internal assembly of the FC (2002/3).

tpc field cage progress report

Documents

meyerepaitresistor rod

meyerepaitfield cage

meyerepaitgas cooling

meyerepaithigh intensity

meyerepaitvoltage divider

resultsoutside of rod

cresistor rod

resultsinside of rod