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Simulating Backgrounds in PEP-II Commissioning 1998-1999

This note assumes you know how to run bbsim and how to change variables in dbio structures in your runtime.db.

The beamline used in pep-ii commissioning in 7/98 and 10/98-2/99 has been put into bbsim. Release 7.8.2 is currently the best choice. Include gnbabar V00-01-00 and gnbpip V00-04-12 or gnbpip V00-04-12-01 and gnbbg V00-05-29-01. If you want to take advantage of the full turtle read, which includes the coul/brem flag and turtle hit info, include gnbpip V00-04-12-01 & beget V00-23-53-01.

There are several flags which must be set in your runtime.db:

  • int use_bkgd 1 (in structure bpuse): this flag improves the tracking of the background rays through the beamline magnetic fields.
  • int use_pcom98 1 (in structure bpuse): this flag turns off the steel endplugs as they don't exist in commissioning.
  • int mode 1 (in structure bpfld): this flag controls Bfield calculation so that only beamline fields are used, not the solenoid
  • real field 0.0 (in structure bdet)
  • int fulltur_read 1 (in structure bpuse): switch this flag on, if you want to read the full set of turtle information (coul/brem flag and turtle hit info)

Here is an example file with the additional items you will need in your runtime.db . Initial sets of TURTLE rays (courtesy of Ted Fieguth) for the HER and LER are available in:

  • ~tlgeld/babardata/98HER_i8m_r8m/
  • ~tlgeld/babardata/98LER_i8m_r8m/

These are HER/LER rays for 98 commissioning run, with an (i=)input at (+ or -)8m and generated with a (r=)range of +-8m (i.e., required to hit somewhere within +-8m of the IP). Each directory has a readme file from Ted to describe the input format and the relevant time window.

Also in those directories are 2000 event files to make submitting batch jobs easier. blah.list.xxxx will read in blah.dat.xxxx.

Here is an example ffread which shows the format necessary to read in the turtle rays.

Simulating Backgrounds in BaBar 1998-1999

This note assumes you know how to run bbsim and how to change variables in dbio structures in your runtime.db.

The final beamline has been put into bbsim. You must use release 7.8.2 or later. If using any 7.8.x, include gnbabar V00-01-00 and gnbpip V00-04-12 and gnbbg V00-05-29-01. You must set the field flag to includ the beamline fields (in your runtime.db):

  • int mode 2 (in structure bpfld): this flag controls Bfield calculation so that beamline and solenoid fields are used

One option is to input the new lost particle rays directly into BBSIM, rather than using the background frames. This might be useful for getting preliminary information on occupancies. Initial sets of TURTLE rays (courtesy of Ted Fieguth) for the HER and LER are available in:

  • ~tlgeld/babardata/98HER_i8m_r8m/
  • ~tlgeld/babardata/98LER_i8m_r8m/

These are HER/LER rays for 98 commissioning run, with an (i=)input at (+ or -)8m and generated with a (r=)range of +-8m (i.e., required to hit somewhere within +-8m of the IP). Each directory has a readme file from Ted to describe the input format and the relevant time window.

Also in those directories are 2000 event files to make submitting batch jobs easier. blah.list.xxxx will read in blah.dat.xxxx.

If you put the turtle rays directly into bbsim, you also need to set the following flag so the turtle ray will track properly through the full beamline:

  • int use_bkgd 1 (in structure bpuse): this flag improves the tracking of the background rays through the beamline magnetic fields.
  • int fulltur_read 1 (in structure bpuse): set this flag only if you want to read the full set of turtle variables
Here is an example file with the additional items you will need in your runtime.db . Here is an example ffread which shows the format necessary to read in the turtle rays.

There are preliminary "98-1nTorr" frames (i.e., normalized to 1A, 1nTorr in each ring) background frames available from these Turtle rays. Information on these testing frames can be found here .

Please contact me if you have any questions, suggestions or information about simulating backgrounds.


This page is maintained by Terry Geld (tlgeld@slac.stanford.edu)

Last modified: Thu Feb 4 14:17:49 PST 1999