DCH high voltageDCH high voltage currentcurrent DRC PMTsDRC PMTs scaler ratesscaler rates IFR high voltageIFR high voltage currentcurrent Fast Control & TimingFast Control & Timing deadtime, L1 rates, deadtime, L1 rates, time wrt injection,time wrt injection,
assoc to bunch in trainassoc to bunch in train Level 3 TriggerLevel 3 Trigger subdetector occupanciessubdetector occupancies Neutron counters Neutron counters scaler ratesscaler rates CsI IP detectorsCsI IP detectors (logarithmic response)(logarithmic response)
All update in small intervals (1-5 seconds)All update in small intervals (1-5 seconds)
Normalizedto Bkg Model
M. Weaver PEP-II MAC Review, 17-18 Jan06
Injection- & trickle- background historyInjection- & trickle- background history
HER injection-quality monitor
LERLER injection-quality monitor
Monitor by integrating SVTRAD diode signals over 12 ms after each injection
SVT electronics are sometimes “upset” by exposures greater than 50 mrad / injection.
M. Weaver PEP-II MAC Review, 17-18 Jan06
Monitor using triggers gated around the passing of the injected bunch (1 s x 15 ms)
Injection contaminates the BaBar physics data sample if backgrounds endure too long
HER injection-quality monitor
LERLER injection-quality monitor
Injection- & trickle- background historyInjection- & trickle- background history
M. Weaver PEP-II MAC Review, 17-18 Jan06
Stored-beam background historyStored-beam background history
DCH current normalized to Jan 04 background data
I DC
H, m
srd/
pred
L1 D
eadt
ime
(%) HER Q5 NEG
outgassing
Beam currentsLimited by
BaBar deadtime
M. Weaver PEP-II MAC Review, 17-18 Jan06
Background sources in PBackground sources in PEEP-IIP-II
Synchrotron radiation Synchrotron radiation (this bkg negligible in PEP-II, but not in KEKB)
Beam-gas (bremsstrahlung + Coulomb)Beam-gas (bremsstrahlung + Coulomb) HEB only: BHbg ~ IH * (pH
0 + PHDyn * IH) Note: p0 = f(T) !
LEB only: BLbg ~ IL * (pL0 + PL
Dyn * IL) Note: p0 = f(T) ! 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)
M. Weaver PEP-II MAC Review, 17-18 Jan06
Background Characterization experiments were performed in Jan’04.
Isolated beam-gas, beam-beam, and luminosity driven backgrounds.
Allows prediction of future background impact on detector performance.
Predictions are still valid in the absence ofabnormal vacuum activity.
Should repeat characterization whenchanges in PEP-II warrant.
Still need to update predictions withnew PEP-II performance projections,but implications are similar.
Tracking efficiency drops by roughly 1% per 3% occupancy
DCHDCH
LER contribution very small
M. Weaver PEP-II MAC Review, 17-18 Jan06
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, 17-18 Jan06
L1R
ate
/ Pre
dict
ion
Run 5a
The trigger rate was effected considerably more than the drift chamber occupancy or current
Run 5b
0
0
3
3
Time
Greater than x2
Scrubbing the newHER Q5 chamber
M. Weaver PEP-II MAC Review, 17-18 Jan06
Dea
dtim
e (%
)
Trigger Rate (Hz)
Front-end Readout (4
buffers)
DCH Feature
Extraction Bottleneck
Deadtime problem was foreseen in DAQ projections
“Phase I” drift chamber electronics upgrade
Installed for Run5a
Addressed the “Front-end Readout” contribution to
deadtime
(factor x2 improvement)
“Phase II” upgrade
Installed for Run5b but not yet activated
Addresses both components sufficiently for the lifetime of
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
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, 17-18 Jan06
Monitoring of single-beam backgroundsMonitoring of single-beam backgrounds
Jul’05 Jul’05
LER current (A) HER current (A)
Take single beam background data opportunisticly to monitor vacuum
Jan’04Model
M. Weaver PEP-II MAC Review, 17-18 Jan06Simulation of luminosity background in the EMC C.
Cohalan
GEANT4 Simulation of Luminosity backgroundsGEANT4 Simulation of Luminosity backgrounds
M. Weaver PEP-II MAC Review, 17-18 Jan06
NeutronNeutronss
A high rate of neutrons is generated from radiative Bhabha interactions. These neutrons are believed responsible for DCH electronics radiation upsets at a rate of 2/hour. A small fraction of these alter the electronics behavior, and data acquisition must be paused to re-configure the electronics.
Turtle simulation of LER scattered particles striking near IP
M. Weaver PEP-II MAC Review, 17-18 Jan06
IP CharacterizationIP Characterization
Use BaBar’s tracking resolution and prime venue for Use BaBar’s tracking resolution and prime venue for measuring important parameters at the IPmeasuring important parameters at the IP
Three analyses each measuring y, *y (see J.Thompson’s talk) dLumi / dz vertexing e+e- and +- events yLumi(z) +- events y’Lumi(z) +- events
(resolution)Production vertices (x,y,z ~ 30m)
Boost trajectories ( ~ 0.6 mrad)
e- beam
e+ beam
M. Weaver PEP-II MAC Review, 17-18 Jan06
BaBar IP measurements reported onlineBaBar IP measurements reported online
Luminous RegionLuminous Region centroids { x, y, z} sizes { x, z } every 10 minutes tilts { dx/dz, dy/dz } dL/dz fit { z, *y } every ~hour
Boost TrajectoryBoost Trajectory mean { x’, y’ } every 10 minutes spread { x’HER, y’HER } every 30 minutes
}
M. Weaver PEP-II MAC Review, 17-18 Jan06
Compare boost trajectory and luminous region tilt
x’boost – dx/dz lumi ≈ full crossing angle
(10’ online measurement)
Moving one beam in a controlled experiment yields
each beam’s x-size(1 day)
L = 68m
L=80m, H=140m
-22.4
xz a
ngle
(mra
d)
-20.6
xz c
ross
ing
ang
le (m
rad)
0
-1
M. Weaver PEP-II MAC Review, 17-18 Jan06
Studies on Luminosity TransientStudies on Luminosity Transient
DCH time resolution allows event DCH time resolution allows event association to RF bucketassociation to RF bucket
Studied many IP parameters along Studied many IP parameters along bunch trainbunch train
z-centroid, sizex,y-centroids, x-sizex’,y’ means and spread
Events
z-centroid x-size
mini-train
mini-trainfull-train
20%
63m
66m
mm
M. Weaver PEP-II MAC Review, 17-18 Jan06
Measuring Coupling at the IP with BaBarMeasuring Coupling at the IP with BaBar
Single BeamCovariance Matrix =
Effect of Coupling on LuminosityReduced overlapBeam size evolution
Effort to Measure Off-Diagonal Elements via Boost – Position Correlations
M. Weaver PEP-II MAC Review, 17-18 Jan06
Summary (I)Summary (I)
Stable-beam (genuine) radiation aborts are ~ 1/day (Run5a) Stable-beam (genuine) radiation aborts are ~ 1/day (Run5a) Vacuum induced Vacuum induced instabilities(?) add to make ~ 4/day (Run5b)instabilities(?) add to make ~ 4/day (Run5b)
Injection backgrounds are monitored and under control Injection backgrounds are monitored and under control Stored-beam bgds (dose rate, data quality, dead time) Stored-beam bgds (dose rate, data quality, dead time)
OK on average – problematic episodes of vacuum activity: “vacuum spikes” and HER thermal
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
No new dedicated experiments performed – OK as long as there are no surprises (e.g. beam-beam backgrounds)
M. Weaver PEP-II MAC Review, 17-18 Jan06
Summary (II)Summary (II)
Main vulnerabilities areMain vulnerabilities are beam-gas backgrounds from HOM-related thermal outgassing as I+,- high dead time associated with data volume & trigger rates (SVT
readout then EMC feature extraction – ultimately may tighten trigger) high occupancy and radiation ageing in the mid-plane of the SVT,
possibly leading to a local loss of tracking coverage. a high flux of ~ 1 MeV neutrons in the DCH (radiation upsets, wire aging
from large pulses, possibly also contributions to occupancy) Background simulationsBackground simulations
BaBar-based IP characterizationBaBar-based IP characterization Increasing amount of measurements reported online Significant amount of offline analysis to understand important
parameters
M. Weaver PEP-II MAC Review, 17-18 Jan06
MDI abstracts submitted to EPAC06MDI abstracts submitted to EPAC06
Monitoring of Interaction-Point Parameters using the Three-Dimensional Monitoring of Interaction-Point Parameters using the Three-Dimensional Luminosity Distribution Measured at PEP-IILuminosity Distribution Measured at PEP-II
B.Viaud, W. Kozanecki, C. O’Grady
Characterization of the PEP-II Colliding Beam Phase Space by the Boost MethodCharacterization of the PEP-II Colliding Beam Phase Space by the Boost Method M.Weaver, W.Kozanecki
Combined Phase Space Characterization at the PEP-II IP using Single-Beam and Luminous-Region Measurements
