Progress on Photon Beam and Simulation Part 1: active collimator Part 2: physics simulations Richard Jones, University of Connecticut GlueX collaboration

Progress on Photon Beam and Simulation

Part 1: active collimatorPart 2: physics simulations

Richard Jones, University of Connecticut

GlueX collaboration meeting May 20-22, 2004, Bloomington

2

Richard Jones, GlueX meeting, Bloomington, May 20-22, 2004

Photon Beam: open issues for the TDR photon source

deformation of thin crystals improved mounting technique

tagging spectrometer conceptual design under revision [talk by J. Kellie] detailed field calculations available [P. Brindza] possible advance-purchase item

photon tagger instrumentation tagging microscope

photon beam instrumentation beam line shielding beam position control photon beam polarimetry

3


I. Active collimator prototype

Tungsten pin-cushion detector used on SLAC coherent bremsstrahlung beam line in

1970’s technology developed at SLAC through several iterations,

refined construction method reference Miller and Walz, NIM 117 (1974) 33-37 SLAC experiment E-160 (ca. 2002, Bosted et.al.) still

uses them, required building new ones performance is known

4


Design was part of the senior project of Connecticut undergraduate

Chris Gauthier

5


Basic design: tungten pins on tungsten wedges

12 cm 5 cm

6


Manufacturing challenge: cutting the pins

challenges to overcome choice of material

too soft, pins bend and break during tool extraction too hard, pins are brittle and break off

how to mount pins in base plate tungsten wire forced into holes – SLAC method 1 machined out of one piece using EDM – SLAC method 2

to the rescue: FSU physics machine shop have their own in-house EDM machine willing to try new things, come up with their own ideas based on drawings from Connecticut, built 2 wedges

raw tungsten – too brittle, pins too fragile machinable tungsten (95%W, 5%Ni+Cu) – excellent result!

7


Courtesy of P. Eugenio

8


Prototype status and plans

Parts for a working prototype are assembled aluminum housing made in Connecticut machine shop one tunsten pin quadrant delivered by FSU data acquisition computer electronics purchased by Jlab and delivered to Connecticut

8-channel sampling ADC card (pci) special preamplifier with pA sensitivity (2 channels)

Still needed to complete project tungsten pins to instrument opposing quadrant (from FSU) boron nitride insulating support (ordered by Jlab, expected 7/04) software to read out currents and filter noise (student project 7/04) couple days of parasitic time in Hall B during photon running

9


II. Physics simulations

Hardware development built and commissioned new GlueX simulations cluster at UConn

Software development (more about this on Friday) upgraded XML geometry database tools to Apache XERCES 2 worked with Curtis to update geometry description of CDC new tools to support use of XML schemas in place of DTD’s

Background studies prior background studies have focused on region upstream of target new information needed to assess design choices for vertex counter geometry for simulations proposed by Werner new results as of this week – more about this from Werner

10


GlueX simulation cluster

parts purchased by Jlab (GlueX R&D funds)

16 AMD 2800+ processors 8 AMD 64-bit opteron processors 1 GB ram per node 20 GB local disk storage per node 5 TB of shared disk storage $28K total cost (incl. rack + UPS)

collaboration access uses web interface (no logins) uses certificates for security browse results with paw ROOT support coming

11


Electromagnetic background study: preliminary results

photon beam

12


background study: preliminary results

photon beam

13


background study: impact profile

14


background study: origin of charges hitting vtx cylinder

inner surface impacts outer surface impacts

15


background study: preliminary

endcap impacts all charged hits over 1 MeV

16


background study: preliminary Latest results are new

still have to be carefully checked removed vacuum pipe from region downstream of target accidentally the air that replaced it has no magnetic field!

Rates are very high downstream of target most important around hole in FDC, Cerenkov, TOF and LGD will set an upper limit on the attainable beam intensity rates far downstream of target sensitive to magnetic field, but Werner’s result is probably accurate for the vertex counter

Backgrounds in each forward detector must be checked important information for the TDR may affect design choices in VTX, FDC and Cerenkov

Documents

Progress on Photon Beam and Simulation Part 1: active collimator Part 2: physics simulations Richard Jones, University of Connecticut GlueX collaboration