the gluex cdc

21 October 2004 The Straw Tube Chamber

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The GlueX CDC

Curtis A. MeyerCarnegie Mellon University

Physics Requirements

Chamber Specifications

Prototype Construction

Future Work

Final Chamber

Summary

Straw Tube Chamber


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CDC

FDC

CDC+FDC

Physics Requirements

p! 1(1800)p ! 2+2-±pMomentum of tracks in the CDC99% Charged particle acceptance

98% Photon acceptance

pions

protons

~1

Ge

V/c

10-60o


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Chamber Requirements

To achieve the overall momentum and vertex goals of the experiment,the CDC needs to achieve:

r» 150-200m z» 2mm

Stereo Layers z=r/tan (st) » 1.4 mm

Charge Division z » 1.5% (2L) » 6 cm

Sweep time should be as short as possible ~600-700ns

Electrostatics need to be very well understood and regulardue to the large Lorentz Angle.

Particle ID using dE/dx for p· 450 MeV/c (proton/ pion)


4BNL EVA Chamber

2m long, 2cm diameter straw tubechamber from BNL.

Electronic Gasmixing system

Scope basedDAQ to Emulate FADC


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Simulations

A very detailed description of the CDC is in HDGEANT, butwe have not written digitization routines yet.

Detailed GARFIELD simulations have been carried out for the CDC, and information on a number of potential gas mixtures have been cataloged.

Detailed Acceptance studies using HDFast have been carried out for the combined CDCFDC system, and show that for typical channels with exotic Hybrids, we have about 99% of 4 acceptance for charged tracks.


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Chamber Mechanics

In order to fully combine both the FDC and CDC for tracking, thematerial in the downstream end-plate of the chamber needs to be minimal.Sense wires: ~3500 ~70 gm tension 245kg

Straw tubes are sufficiently rigid to fully support this load.Straw tubes provide very uniform electric fieldsGarfield studies show that we can achieve the drift time limits.

Guard wire option: ~14000 ~200 gm tension 2800kgEndplates and shells would need to be thick to support this! Probably more than 4 per sense wire to get a uniform field.Corners in the cells will produce large drift times.


7Chamber Design

23 Layers from 14cm to 59cmLayer 1-4 StraightLayer 5-6 +6± stereoLayer 7-8 -6± stereoLayer 9-13 StraightLayer 14-15 +6± stereoLayer 16-17 -6± stereoLayer 18-23 Straight

Active length between 1.75m and 1.97mrmin = 14.0cm rmax=57.8cm

Upstream endplate: 0.95 cm thick Al tooling plate Al donuts All electrical connections

Down stream endplate: 0.50 to 0.60 cm thick Al or .90cm thick G10 Delrin donuts Possible termination circuits

Inner shell: Thin Carbon fiber – mostly protection

Outer shell: Carbon fiber or fiberglass Alignment and protection

3250 Wires


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ElectronicsStraw Tube

High Voltage

Pre-Amp125MHz FADC

8ns wide time bins

time

t» 2-3ns

Tracks

straw tube

Need 10-bit ADC resolution

ADC yields dE/dx information

JETSET: NIM A367, 248 (1995)dE/dx at 10% resolution in strawtubes.

FADC: IU/JLab

Preamp: Alberta/JLab


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Resolution

Contributions to Resolution

Geometrical Precision 40mGravitational Sag 56mTiming Resolution 45mElectrostatic Deflection 10mGas Diffusion 120m________________________Total » 145m

90-10 Ar-CO2

tmax» 0.5s

Radius [cm]

Tim

e [s

]

We have a gas mixture that shouldwork, but we would like to optimizethis .

Would like to use the same gas inboth the FDC and the CDC.


10

Gas Leaks

A problem with straw tube chambersis that the glue joints leak.

Designed, built and tested a feedthrough system that forms a solidglue seal.

System has held several psi overpressurefor nearly a year.

Donut


11Prototype Construction

The difficult part of the straw-tube chambers are the 6± stereolayers. Every step involving these has been a challenge with itsown problems to solve.

Compound angles in machining of the endplates.

Aligning tubes in the chambers.

Gluing tubes together for structural support.

Better Clamshell clamps will be needed for the final chamber.

The Mylar tubes are quite delicate, while it appears thatKapton is more robust, but MORE expensive.


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Stringing The Chamber

Select tube Cut to length Glue donut

Glue in chamber Magnetic Feeds

Pneumatic crimper

Vertical stringing


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Prototype Construction


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Prototype Testing

Wire tensions are accurate and reproducible. We still need to do long-term stability tests.

Mechanical Robustness tests will start as the chamber istaken off the stringing stand.

We are close to being able to perform high-voltage and signal tests.

2004 2005 3rd 4th 1st 2nd 3rd 4th

Chamber Assembly and StringingHigh Voltage Tests

Signal Tests

Structural Tests

Kapton Tubes


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Final ChamberMachine Endplates in industryAcquire Shells Machine Al and Delrin DonutsAcquire Crimp pinsAcquire Straw tubesAcquire Wire

Parts need to be spec’d, orderedand checked.

Tube building takes about 15 minutes per tube (1 person)

Tube installation takes about 15 minutes per tube (2 people)

Tube stringing takes about 15 minutes per tube (2 people)

Electrical and gas hookup times are still not definitive.

3 to 3.5 year to build the final chamber


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Summary

The CDC together with the FDC forms a complete trackingpackage for the GlueX detector that covers roughly 99% of 4 .

The most challenging construction detail of the chamber isthe stereo layers.

There are still some issues with aligning tubes that need bettertools.

Test Kapton tubes in prototype. Based on what we have seenwith samples, these appear a better choice.

Settle on final length based on Monte Carlo (175cm – 200cm),this has little or no impact on construction.


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Task Year 1 Year 2 Year 3Tool ConstructionDesign and Procure EndplatesAcceptance Checks on platesProcurement of feed throughsProcurement of wires and pinsAcceptance of partsProcurement of on-chamber electronicsTests of electronicsConstruction SetupChamber StringingGas System InstallationElectronics InstallationChamber TestsDelivery of Chamber

Chamber Schedule

Best estimate is 3.5 years from start of procurement to delivery Extra Manpower

the gluex cdc

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