Machine-Detector Interface (MDI) report Presented by M. Weaver, SLAC Operational issues radiation aborts radiation-dose and background monitoring Background characterization characterization experiments long-term projections & vulnerabilities Simulations G4 development status
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Presented by M. Weaver, SLAC
HER injection-quality monitor
Monitor using injection-gated triggers (1 ms x 15 ms)
Injection- & trickle- background history
EMC trigs (always on) LER trickle
DCH trigs LER trickle
EMC trigs (always on) HER trickle
DCH trigs HER trickle
DCH current normalized to Jan 04 background data
SVT ocp’cy @ f = 0 (LEB-sensitive)
DCH L1 rate
Step 2: L & beam-beam terms
EMC cluster multiplicity
SVT occupancy (FL1 M01-f)
When combined, higher trigger rates and long read-out time leads to unacceptable deadtime, driven by the DCH
Background strongly - dependent
By 2007 predict 80% chip occupancy right in MID-plane
In layer 1, 10% will be above 20% occupancy
Integrated dose will be more than 1 Mrad/year by 2007SVT
Background now is ~75% HEB [LEB negligible (!)]
In 2007, it will be 50% HER, 50% L
B Petersen N. Barlow M. Cristinziani/T. Glanzman J. Malcles
Evolution of HER single-beam background, 2002-04
Regularly activating NEGs & TSPs does help !
We should continue to take advantage of single beam opportunities to monitor the background.
P. Roudeau, A. Stocchi, W.K. (preliminary)
Turtle Simulation :
e+ e- e+e-g Background
- z (m)
Electromagnetic shower debris or…
EMC default digi map: luminosity background (N. Barlow)
Measurements appear consistent with Turtle radiative Bhabha simulation + GDR cross sections. Projected neutron rates may affect detector electronics – depends upon neutron energy spectrum.
Beam-gas background from the HER (and LER)
Where do scattered e-come from ?
Where do scattered e-hit?
-25.2 m from IP
Results are based on an older LER deck (’98) with a tune of 0.57 (in x).
...at least in the simulation
basically because of the phase-advance relationships reduce this to a one-turn problem, and assuming the impact on LEB lifetime remains manageable.
This study should be redone with the new LER deck & current x-tune of 0.51.
Vertical tails are not an issue (in the LER)
Pre-trickle collimator-scan data remain to be analyzed.
However, the +25 m collimator
can’t replace existing PR04 collimators in some corners of phase space
provides no protection against Coulomb scatters between PR04 and PR02
Both horizontal and vertical b-tron tails will be studied for the HERBeam-beam collimation study: summary
Continued BaBar involvement in Accelerator Performance Improvements (I)