# Presentation: 157376

## Detector Construction of the Forward Proton Detector at D0

- Michael Strang
- University of Texas at Arlington

-  Diffractive Events
-  FPD Layout
-  Detector Construction
-  Status

- APS April Meeting 2001

## Diffractive Event Topologies

- Cross section for elastic scattering can be written as:

- This has the same form as light diffracting from a small disk

- APS April Meeting 2001

## FPD Layout

- Series of 18 Roman Pots forms 9 independent
- momentum spectrometers allowing measurement
- of proton momentum and angle.
** **1 Dipole Spectrometer (** ****p**** **) min
** **8 Quadrupole Spectrometers  (**p****  **or ** p**,  up or down,
** **left or right) t > tmin

**Q****4**

**D**

** ****S**

**Q****2**

**Q****2**

**Q****3**

**Q****3**

**Q****4**

**S**

**A****1Q**

**A****1S**

**A****2Q**

**A****2S**

**P****1Q**

**P****2S**

**P****1S**

**P****2Q**

**p**

**  ****Z(m)**

**A****D2**

**A****D1**

**  ****Detector**

**  ****Bellows**

** ****Roman**
**    ****Pot**

**23**

**33**

**59**

**33**

**23**

**0**

**57**

- APS April Meeting 2001

## Detector Needs

- Position resolution of 100μm
- Beam dispersion and uncertainty in beam position make better resolution unnecessary
-  Efficiency close to 100%
-  Modest Radiation Hardness
- Operates at 8 from beam axis, 0.03 MRad yearly dose expected
-  High Rate capability
- Active at every beam crossing
-  Low background rate
- Insensitive to particles showering along beam pipe
-  Small dead area close to the beam
- Protons are scattered at very low angles, acceptance is very dependent on position relative to beam
-  Scintillating Fiber detector meets these needs

- APS April Meeting 2001

## Detector Setup

- 4 fiber bundle
- fits well the
- pixel size of
- H6568 16 Ch.
- MAPMT
- 7 PMT’s/detector
- 17.42 mm active
- area

**U**

**U’**

- Six planes
- (u,u’,x,x’,v,v’)
- of 800 m
- scintillating
- fibers
- (’) planes
- offset by 2/3
- fiber

- 20 channels/plane(U,V)(’)
- 16 channels/plane(X,X’)
- 112 channels/detector
- 18 detectors
- 2016 total channels
- 4 fibers/channel
- 8064 fibers
- 1 250 m LMB
- 	fiber/channel
- 8 LMB fibers / bundle
- 252 LMB bundles
- 80 m theoretical
- 	resolution

- APS April Meeting 2001

## Detector Components

- _Fibers_
- Scintillating fiber is spliced to clear fiber
-  Increased halo background with scintillating only
-  Light output improved due to longer attenuation length
- of clear fiber
-  Cross talk is reduced
-  Fibers produced by Bicron
-  0.80 mm square multiclad fiber emitting in blue 
-  Square fiber can only be polished using ice
- polishing method at FermiLab Lab 7
-  After polishing fibers are inspected for deformity
- and cladding damage and repolished if needed

- Mirrored side

- 4fibers  PMT

- APS April Meeting 2001

## Detector Components (II)

- _Frames _
- Cast at FermiLab Lab 5 plastics shop
-  Original aluminum machined piece is molded and
- production pieces are cast in polyurethane

- APS April Meeting 2001

## Splicing

-  Splicing being completed at UTA
-  Fibers spliced using a version of the MSU
- splicing machine modified for square fibers
-  With proper setup, light transmission through
- splice point of over 90% possible
- Afterwards, splice point is sensitive to bending
- stresses so care must be taken
-  Shrink tubing cannot be used to strengthen splice due
- to space constraints

- APS April Meeting 2001

## Construction

-  Being completed at UTA
-  Four fibers are aligned together in the frame to     	make a channel
-  X frame also includes trigger scintillating rod
- Bicron optical epoxy is used to secure the fibers 	into the frame once completely assembled
-  After curing, channels are mapped to appropriate 	location in cookie, PMT calibration fibers 	are included, lengths are measured and 	final gluing with optical epoxy is done

- APS April Meeting 2001

## Hit Reconstruction

-  This event (from Engineering Run data)
- represents a hit in our detector at the location:
- 	xd = 5.6 ± 0.4 mm
- 	yd = 3.8 ± 0.4 mm

- APS April Meeting 2001

## Status

- All fibers and frames have been delivered
- Currently have 7 complete detectors
- Working on 8th
- Expect to complete 10 by mid-May
- 10 detectors will be installed this Summer

- APS April Meeting 2001