APS April Meeting 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 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 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 > t min Q4Q4 D S Q2Q2 Q2Q2 Q3Q3 Q3Q3 Q4Q4 S A 1Q A1SA1S A 2Q A 2S P 1Q P 2S P 1S P 2Q p p Z(m) A D2 A D1 Detector Bellows Roman Pot p Beam pFpF P

APS April Meeting 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 Detector Setup 4 fiber bundle fits well the pixel size of H Ch. MAPMT 7 PMT’s/detector 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  m LMB fiber/channel 8 LMB fibers / bundle 252 LMB bundles 80  m theoretical resolution

APS April Meeting 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 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 Scint Fibers 800  m Clear fiber Mirrored side 4fibers  PMT

APS April Meeting 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 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 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 Hit Reconstruction This event (from Engineering Run data) represents a hit in our detector at the location: x d = 5.6 ± 0.4 mm y d = 3.8 ± 0.4 mm

APS April Meeting 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