photon tagging in the hall d beamline james mcintyre university of connecticut 13 may 20101 gluex...

GlueX Graduate Student Workshop Newport News, VA

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Photon Tagging in the Hall D Beamline

James McIntyreUniversity of Connecticut

13 May 2010


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Outline

• How we tag photons• Photon production• Tagger Microscope– Components– Construction

13 May 2010


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• Our interest is in determining the energy of the photons which produce an event in the target.

• The energy of an electron that produced (via bremsstrahlung) a photon of interest is measured so that the counterpart photon can be “tagged” with a correct energy.

• Things to consider:– Not all photons produced will create a usable event in the

target.– Not all electrons will produce a photon.– Need a way to limit & filter accidental tags and noise from the

data stream.• Limiting – Occurs due to our design choices.• Filtering – Statistically process the data stream.

13 May 2010

Tagging


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Photon Production• As the electrons pass through the 20 µm diamond radiator

photons can be produced via bremsstrahlung.• The angle of deflection off the beamline varies.

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• Distance between the Tagger Microscope and Target is ~ 300 feet.

• Over such a large distance even small angles of deflection become considerable.

13 May 2010

Hall D Beamline


613 May 2010

~97 Ft41 Ft~161 Ft~91 Ft

Location of TargetLocation of Tagger Microscope

Hall D Beamline

e- Beam


713 May 2010

e- Beam

Tagger Magnet

Tagger Area

Photon Beam

e- Beam


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• We can use the deflection to our advantage.– Use collimator to filter out photons that have large angles.– Use Scintillating Fibers (SciFi) size to our advantage.

• The electron which produced a photon with a large angle will also have a larger angle.

• Based on Monte Carlo simulations SciFi length and cross-sectional area was selected to provide optimum filtering of incoming electrons (along with other considerations).– 2 mm square multi-clad fibers– 2 cm long

13 May 2010

Tagging


913 May 2010

Tagging


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• Scintillating Fibers– Fast Green Scintillator (BCF – 20)– Decay time 2.7 ns• Other faster fibers were considered but not chosen due

to problems such as shadow signal after event, etc.

• Waveguide– BCF-98– ~23 inches long per channel

13 May 2010

Fiber Selection


1113 May 2010

Prototype of Tagger Microscope


1213 May 2010

Parallel Railing System

Parallel Railing Unit


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13 May 2010

• Ability to adjust bundle angle to permit alignment with electron beam.

• Step motors permit 3-point adjustment of railing height & angle (remotely).


1413 May 2010

Bundle Support Unit (aka Pop-Sickle Stick)

• 5x5 Bundle will mount on it via epoxy.• Permits adjustment of bundle angle.• Nuts on the underside of the rails will secure unit in

place.



1513 May 2010

Fiber Array (Full Scale)

Full Scale Tagger Microscope• Fiber Array

• 500 Fibers• 20 – 5x5 Fiber Bundles• Note: Prototype will only have a single bundle (25 fibers) of which only 20 channels will be utilized.

• 5 horizontal rows• Allow for proper alignment to the incoming beam by using all channels, then secure all except one

row during the test runs.• Provides longer operational lifetime, since radiation damaged fibers can be shifted via the step

motors (instead of being changed out) to keep running using another viable row.

• 100 vertical rows• Determines the amount of curvature of the electron due to the Tagger Magnet, therefore allowing

us to calculate its energy and thus know the energy of the counterpart photon created during bremsstrahlung.

End on view. The electrons would be going into the page.


1613 May 2010

Gluing Station

Gluing Station• Allows for close alignment of the two fibers• Permits fine adjustment of the gap between the fibers• Al construction allows for quicker curing on a heat plate

Gap Adjustment Screw


1713 May 2010

Polishing: End-Mill to paper sanded

Sanded fibers (400 grit)

Straight edge when sanded (in contrast to the rounding shown above)

Prep for Gluing (Old vs. New)


1813 May 2010

Glued Fiber


1913 May 2010

Painting Fibers

Glued fiber joint showing light transmission.

Air Gun used to paint the individual fibers after gluing.


2013 May 2010

Bundle of Fibers

Glued fiber bundles (3x3 practice bundles)• Foreground: Trial bundle with painted individual fibers. BC-600 epoxy was used.• Background: Unpainted trial bundle using Elmer’ Glue.

Tin Foil


2113 May 2010

Splicing Fibers

MSU Splicing Unit• Most promising way to connect SciFi to Waveguides

• As strong as a single fiber• Quick production (once setup correctly)

• Uses a high intensity lamp to heat the fiber to the melting point and fuse them• Was made for round fibers

• Need ferrule for square fibers to maintain shape during slicing

Use of MSU Splicing Unit courtesy of Ron Richards


2213 May 2010

Digital Control Board

Backplane Board Amplifier

Board

Electronics

Electronics• Backplane is secured to the top plate via six 6-32 machine screws.• A Sponge Gasket provides a light seal for the penetration of the electronics.• Not pictured – Card Guides and Chimney


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Electronics

Card Guide

Backplane Board

Chimney

WaveguideSiPM

Amplifier Board96 Pin Euro Connector

Amp Board Guard

Amplifier Board Guard & Guides/Chimney• Amp Board Guard protects SiPMs by preventing rubbing with the waveguides and other components.• Card Guides/Chimney provide for alignment with respect to the waveguides, both vertical and horizontal.• Designed to allow for ease of fiber mounting and removal.


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Electronics

Amp Board Guard SiPM

Leveling strip


2513 May 2010

Summary• Measuring electron energy via deflection in a magnetic field• Tagging photons • Components of the Tagger Microscope

photon tagging in the hall d beamline james mcintyre university of connecticut 13 may 20101 gluex...

Documents

va slide

tagging slide

hall d beamline slide

photon tagging

fiber selection slide

counterpart photon

electron beam

bundle angle