Proposed Plan of Work and Budget for Linear Collider Detector R&D on a Scintillating Fiber Intermediate Tracker to Provide Timing Information

The performance and capabilities of the charged particle
tracking in the TPC-based large detector can be enhanced
by the presence of an intermediate tracker at radii just below
the inside radius of the TPC.  Such a device would link tracks
between the vertex and central tracking detectors, improve pattern
recognition, and provide a reliable and stable measurement points
close to the TPC for use in the calibration of the TPC and monitoring
variations of its characteristics with time.  Possibly most
importantly, a scintillating fiber tracker can offer high-precision
timing of tracks in events.

The current machine design provides beams composed of trains of
many ($>100$) bunches with bunch spacings of $\sim 1.4$~ns.  Large rates (10's of nb) of two
photon interactions are expected both from interactions of virtual photons
from each beam and virtual photons with real photons from beamstrahlung. The overlap
in the other tracking devices of the much more prevalent two-photon events
resulting in ``mini-jets'' with the more interesting $e^+e^-$ interaction events can be a problem if bunches
are not identified in time.  A scintillating fiber intermediate tracker coupled by clear fiber to visible
light photon counters (Si:As devices manufactured by Boeing
with a fast response time of less than 100~ps) read out by the
SVXIIe chip can achieve time resolutions less than 1~ns to associate tracks with individual
bunches as well as complement time measurements in the TPC.

Simulation studies already performed show significant impact on Higgs
events with missing energy when 2-photon events from prior or
subsequent bunches are overlaid on top of the event of interest.  A
system with sub-nsec timing could identify from which bunch tracks came.

Draft Proposed Plan of Work

  In collaboration with Mike Hildreth et al. at Notre Dame, investigate bunch
id timing using a intermediate scintillating fiber tracker.
Specifically, in a proposed system, two or three layers of scintillating fibers would be
physically mounted directly on the inner radius carbon fiber structure
of a TPC. Readout using visible light photon counters can potentially
result in a system timing resolution with the needed resolution.
We would also investigate the utility of having fibers mounted on the
outer radius of a TPC with further simulations.

  A 384 channel system (3 layers of fibers, length of 60 cm) mounted to a
carbon fiber mockup of the inner radius support structure of a TPC,
in conjunction with refurbished prototype/reject ATLAS transition radiation tracking
modules (with carbon fiber shells) will be used in cosmic ray tests
with differing scintillating fiber formulations and latest VLPC's from
Rockwell to confirm needed overall system timing and position resolutions.

  Follow up studies could include tests of embedding such fibers in to
calorimeter detector systems to also allow timing of shower clusters
from neutral particles.  This would be done collaboratively with
groups investigating calorimeter systems.

Draft Budget (initial year, equipment, parts, material only; personnel and
travel through DoE base contract)
 
 

	Item	Cost
1.	Scintillating fiber + construction of ribbons, different formulations    (3 layers, 128 fibers each, 60 cm long)	$16k
2.	Clear fibers, optical connectors	$8k
3.	Visible light photon counters [VLPC'S] and readout     SVX version (explore latest versions available from Rockwell/Boeing)	$25k
4.	Cryogenics and dewar for VLPC operation, consumables     (refurished FNAL equipment? departmental dewar)	$20k
5.	Data Acquisition	$10k
6.	Prototype carbon fiber arc shell     (mockup of inner barrel of a LC detector TPC)	$10k
6.	Test Equipment	$10k
8.	Refurbished ATLAS transition radiation straw     tracker modules + consumables	$20k
	TOTAL WBS Items	$119k