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beam-gas x- term: BLHbg ~ cLH * IL * IH (LEB+HEB, out of collision) (?)
Luminosity (radiative-Bhabha debris) – Luminosity (radiative-Bhabha debris) – major concern as L major concern as L BP ~ dP * L (strictly linear with L)
Beam-beam tailsBeam-beam tails
from LER tails: BL, bb ~ IL * fL(L,H +/-)
from HER tails: BH, bb ~ IH * fH(L,H +/-)
Trickle background: BTrickle background: BLi Li ,, BBHiHi (injected-beam quality/orbit + beam-beam)
Touschek: BTouschek: BLTLT (signature somewhat similar to bremstrahlung; so far small)
HER LER LuminosityNOW 1.2 A 1.9 A2004 1.6 A 2.7 A2005 1.8 A 3.6 A2006 2.0 A 3.6 A2007 2.2 A 4.5 A
7.2x1033 cm-2s-1
12.1x1033 cm-2s-1
18.2x1033 cm-2s-1
23.0x1033 cm-2s-1
33.0x1033 cm-2s-1
PEP-II parameter projections
Tracking efficiency drops by roughly 1% per 3% occupancy
DCHDCH
LER contribution very small
60 L
M. Weaver PEP-II MAC Review, 13-15 Dec 04
DCH + TRGDCH + TRG
When combined, higher trigger rates and long read-out time leads to
unacceptable deadtime, driven by the DCH
3-step strategy
DCZ trigger (ready) Waveform decimation
(was implemented Summer ’04)
DCH DAQ upgrade (Summer 05)
+DCZ
M. Weaver PEP-II MAC Review, 13-15 Dec 04
It has been realized that in the SVT (but not in other subdetectors), a large fraction of the “Luminosity” background is most likely due to a HER-LERLER beam-gas X-term (but: similar extrap’ltn).
SVTSVT Integrated dose will be more than 1 Mrad/year by 2007
Backward:
Forward:
TopEast West Bottom
TopEast West BottomN
OW
2004
2005
2006
2007
Background now is ~75% HEB
[LEB negligible (!)]
In 2007, it will be 50% HER, 50% L
Background strongly - dependent
By 2007 predict 80% chip occupancy right
in MID-plane
In layer 1, 10% will be above 20% occupancy
M. Weaver PEP-II MAC Review, 13-15 Dec 04
Given that future backgrounds have serious implications for Given that future backgrounds have serious implications for detector performance, can anything be done to mitigate detector performance, can anything be done to mitigate them?them?
Beam-gas backgrounds : manage residual gas pressureBeam-gas backgrounds : manage residual gas pressure
Luminosity backgrounds : learn how to shieldLuminosity backgrounds : learn how to shield
Beam-beam backgrounds : learn how to collimateBeam-beam backgrounds : learn how to collimate
How will the IR upgrade affect each of these?How will the IR upgrade affect each of these?
Need to turn to simulation to improve our understanding Need to turn to simulation to improve our understanding and test mitigation strategies.and test mitigation strategies.
M. Weaver PEP-II MAC Review, 13-15 Dec 04
Evolution of HER single-beam background, 2002-04Evolution of HER single-beam background, 2002-04B Petersen N. Barlow
M. Cristinziani/T. Glanzman J. Malcles
Jan 2004
Apr 2004
Feb 2002Feb 2002
SVT occupancy
Jan 2004EMC clusters
Apr 2004
Regularly activating NEGs & TSPs does help !
We should continue to take advantage of single beam
Large-amplitude, horizontal b-tron tails originating at the IP can be Large-amplitude, horizontal b-tron tails originating at the IP can be effectively curtailed at + 25 meffectively curtailed at + 25 m
...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 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 HERBoth horizontal and vertical b-tron tails will be studied for the HER
M. Weaver PEP-II MAC Review, 13-15 Dec 04
Major background source:Major background source: thermally thermally-enhanced -enhanced beam-gasbeam-gas in incoming LER straight
Sensitive to LER current; several time constants in a time-dependent mix
Action: removed several NEGs and collimator jaws
Pressure at low currents may be worse now, but less susceptible to heating
SVT dose + occupancy (E-MID); minor impact on dead time
in incoming HER straight sensitive to HER current, very long time constants
BaBar dead time + SVT occupancy (W-MID)
in (or very close to) the shared IR vacuum system sensitive to both beam currents; at least 2 time constants
suspect: NEG + complicated IR ‘cavity’ (Q2L Q2R) + HOM interference
BaBar dead time + SVT occupancy (W-MID + E-MID)
HOM dominant heating mechanismHOM dominant heating mechanism mostly long to very long time constants (30’-3 h): suggests low power
sensitive to: bunch pattern, VRF, collimator settings, Z(IP), hidden var’s
Fast monitoring of machine backgrounds Fast monitoring of machine backgrounds available online in PEP-II CS available online in PEP-II CS [MW, C’OG, AP, GDF,...]
Forward end Fe shielding wall (may allow better collimation elsewhere)
BaBar involvement in Accelerator Performance Improvements (II)BaBar involvement in Accelerator Performance Improvements (II)
M. Weaver PEP-II MAC Review, 13-15 Dec 04
Summary (I)Summary (I)
Stable-beam (genuine) radiation aborts are down to ~ 1/dayStable-beam (genuine) radiation aborts are down to ~ 1/day
Injection backgrounds under control, expect even better in Run5 Injection backgrounds under control, expect even better in Run5
Stored-beam bgds (dose rate, data quality, dead time) Stored-beam bgds (dose rate, data quality, dead time) OK most of the time –watch for thermal outgassing, esp. HER
Background characterization experiments Background characterization experiments Highly valuable in identifying the origin, magnitude & impact of single-
& two-beam backgrounds – be opportunistic
Maintain a measure on the projected backgrounds – impacts detector remediation/upgrades with long lead times
G4 Simulation progressing; anticipate better understanding and G4 Simulation progressing; anticipate better understanding and correlation of sources with detector responsecorrelation of sources with detector response
Collimation simulations can direct future background Collimation simulations can direct future background improvementsimprovements
M. Weaver PEP-II MAC Review, 13-15 Dec 04
Summary (II)Summary (II)
In the medium term (2005-07), the main vulnerabilities areIn the medium term (2005-07), the main vulnerabilities are beam-gas backgrounds from HOM-related thermal outgassing as I+,- high dead time associated with DCH data volume & trigger rates
(addressed by DCH elx upgrade)
high occupancy and radiation ageing in the mid-plane of the SVT, possibly leading to a local loss of tracking coverage.
reduce the HER single-beam background back to 2002 levels (/1.5-2) ?
a high flux of ~ 1 MeV neutrons in the DCH (wire aging from large pulses, possibly also contributions to occupancy)
Background simulationsBackground simulations large investment in reviving/updating tools + rebuilding the group
‘almost’ ready to evaluate backgrounds in IR upgrade
manpower limited
BaBar-based accelerator performance enhancementBaBar-based accelerator performance enhancement common BaBar-PEPII diagnostics greatly improved, starting to pay off
very significant involvement of BaBarians in beam instrumentation & simulation
M. Weaver PEP-II MAC Review, 13-15 Dec 04
MDI abstracts submitted to PAC05MDI abstracts submitted to PAC05
Predicting PEP-II Accelerator-Induced Backgrounds Using TURTLEPredicting PEP-II Accelerator-Induced Backgrounds Using TURTLE R. Barlow, W. Dunwoodie, W. Kozanecki, S. Majewski, P. Roudeau, A. Stocchi , T. Fieguth & J. Va’vra
Modelling Lost-Particle Accelerator Backgrounds in PEP-II Using LPTURTLEModelling Lost-Particle Accelerator Backgrounds in PEP-II Using LPTURTLE T. Fieguth, et al.
GEANT4-based Simulation Study of PEP-II Beam Backgrounds in the BaBar Detector at the SLAC B-Factory
W. Lockman, D. Aston, N. Barlow, N. Blount, M. Bondioli, G. Bower, G. Calderini, B. Campbell, M. Cristinziani, C. Edgar, W. Kozanecki, B. Petersen, S. Robertson, D. Strom, G. Wormser, D. Wright
Beam-induced Neutron Fluence in the PEP-II Interaction Region G. Bower, W. Lockman, J. Va'vra, D. Wright
Measurement of the Vertical Emittance and beta Function at the PEP-II Interaction Point Using the BaBar Detector
J. M. Thompson & A. Roodman
Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to e+/- Bunch-Length Determinatione+/- Bunch-Length Determination
B.Viaud, W. Kozanecki, C. O’Grady, M. Weaver
Experimental Study of Crossing-Angle and Parasitic-Crossing Effects at the PEP-II e+e- Collider
W. Kozanecki, Y. Cai. I. Narsky, M. Sullivan & J. Seeman
M. Weaver PEP-II MAC Review, 13-15 Dec 04
Measurement of the Vertical Emittance and beta Function at the PEP-II Interaction Point Using the BaBar Detector
J. M. Thompson & A. Roodman
Measurement of the Luminous-Region Profile at the PEP-II IP, and Measurement of the Luminous-Region Profile at the PEP-II IP, and Application to e+/- Bunch-Length DeterminationApplication to e+/- Bunch-Length Determination
B.Viaud, W. Kozanecki, C. O’Grady, M. Weaver
Experimental Study of Crossing-Angle and Parasitic-Crossing Effects at the PEP-II e+e- Collider
W. Kozanecki, Y. Cai. I. Narsky, M. Sullivan & J. Seeman