W. KozaneckiPEP-II MAC Review, 9-11 Oct 03 Machine-Detector Interface Issues Machine Backgrounds, Present & Future BaBar involvement in Accelerator

W. Kozanecki PEP-II MAC Review, 9-11 Oct 03

Machine-Detector InterfaceMachine-Detector Interface

IssuesIssues

Machine Backgrounds, Present & FutureMachine Backgrounds, Present & Future

BaBar involvement in Accelerator Performance ImprovementsBaBar involvement in Accelerator Performance Improvements

SummarySummary

W. Kozanecki, CEA-Saclay


The IssuesThe Issues

Backgrounds operational efficiency (this coming run)

long-term projections (2005 & beyond)

New IR design background simulations: can BaBar live with predicted levels?

make it all fit (unavoidable hardware changes!) [this topic likely to grow in importance]

Accelerator Performance Improvements background remediation

beam dynamics

instrumentation

IR geometry, orbits & optics

BaBar-based accelerator diagnostics


Backgrounds: what has happened so farBackgrounds: what has happened so far

Try & revive the ‘Try & revive the ‘Background GroupBackground Group’’ Strong (and largely successful) effort at

awareness-raising in BaBar (“work on backgrounds? why?”)

recruiting help

Identified subdetector background contact persons (SBC)

Regular MDI meetings (~ every other week)

Background WorkshopBackground Workshop: 22-24 Sep 03: 22-24 Sep 03http://www.slac.stanford.edu/BFROOT/www/Public/Physics/bgd2003_workshop/agenda_items/agenda.html

In-depth review of radiation-abort policies: “make BaBar & PEP-II transparent to each other”

Run-4 backgrounds: operational issues, vulnerabilities, long-term projections

Launch the background-simulation effort


Background Sources I Background Sources I (())

Synchrotron-radiation X-raysSynchrotron-radiation X-rays Power: mostly separation dipoles

Background: mostly HER IP quadrupoles

Duck it if you can! else mask it, but watch out for multiple bounces

Masking very effective: SR backgrounds not a problem in BaBar so far

Cool it well - or else!

Lost-particle backgroundsLost-particle backgrounds Bremsstrahlung: e + gas -> e’ + (E’ < E)

By now, almost exclusively from the last few (tens of) m ==> vacuum!

Coulomb scattering: e + gas -> e’ (E’ = E, but )Potentially from the whole ring, depending on limiting apertures and on pressure profile. In practice no longer an issue

Touschek : similar to bremsstrahlung BaBar: neglected so far. Should be checked for very-high current operation.

Luminosity (e+ e- => e+’ e-’ )

Elm shower debris (radiation + occupancy) + beam-wall p’s (trigger)


# Xtls

> 10 MeV

Single-beam backgroundsSingle-beam backgrounds

EMC

vs. I+, I-

IDCH vs. I+

Two-beam backgroundsTwo-beam backgrounds

% occpcy (> 1 MeV)

EMC vs. I

(I+ = 1100)-

L1 trigger rate vs. I- (I+ = 1100)


Background ProjectionsBackground Projections (based on bgds measured in 2000, then 2002)

High-Luminosity Model (JS, PEP-II AP Note 130) combined with ( - I- + - I-2 ) + (+ I+ + + I+

2 ) + L

Drift Chamber Bakground Projection (July 2000 characterization)

Beam-current timeline model

0

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Avera

ge c

urr

ent

(A)

HER

LER

Luminosity timeline model

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2000 2001 2002 2003 2004 2005?Calendar year

Avera

ge L

(10

33

)


SVT SVT Bakground Bakground ProjectionProjection

Pain threshold: ∫dose ~ 2 MRad

Horiz. plane: ~ 2 MRad by 2003-4, then 0.5 - 1 MRd/y

Other : ~ 0.25 MRad by 2004, then ~ 0.1 MRad/y

DIRC DIRC Bakground Bakground ProjectionProjection

Pain threshold: PM rate ~ 200 kHz Pain threshold: PM rate ~ 200 kHz

(dead time ~ % @ 300 kHz, 20% @ 500 kHz)

Note how different the relative contributions are between subdetectors

July 2000 characterization


Recent background history: DCHRecent background history: DCH

Compare measured DCH background to that expected

at the same LER currentLER current, HER current & LuminosityLuminosity,

based on the Feb. 2002 characterization


Background Sources IIBackground Sources II (())

Lost-particle backgrounds Lost-particle backgrounds (continued)

Beam-beam (?) tails ~ Coulomb-like signature ==> collimation ? ( LER !)

elm shower debris in incoming detector straight (esp. LER?)

‘‘steady state’ : DCH, IFR – but also SVT (dose + occupancy)steady state’ : DCH, IFR – but also SVT (dose + occupancy)

Spikes & fluctuations DCH, TRG

Radiation burstsRadiation bursts spikes (“fast aborts”)

trapped events

Injection backgroundsInjection backgrounds 30-90% of SVT dose

45% of EMC dose (CsI calorimeter)

~ 50% radiation aborts


Recent background history: SVT, IFRRecent background history: SVT, IFR

SVT IFR endcap

predicted (2002)

measured


DCH current

steady-state level

HER lifetime

400 sec

Manual abort

Radiation burstsRadiation bursts

Fast (auto) abort


Injection BackgroundsInjection Backgrounds

FW FE BW BETOP 81 (14%) 52 (41%) 100 (9%)MID 374 (63%) 333 (67%) 488 (66%) 215 (65%)BTM 90 (30%) 59 (38%) 82 (20%) 58 (45%)

25 (55%)

(Numbers are in krad, (%) is of dose in stable beams)

SVT Radiation dose from January to June 2003


SR + beam gas + “Lumi” (eSR + beam gas + “Lumi” (e++ee-- e e++ e e-- ) (“traditional”)) (“traditional”) not an issue ’05 w/ present IR geometry (& * !) however beam-gas in the LER may become a major contributor to the SVT

integrated dose occupancy

once the LER current is raised significantly

Beam-beam tails (SVT occupancy, DCH spikes, dead-time Beam-beam tails (SVT occupancy, DCH spikes, dead-time burstsbursts, IFR , IFR currents) a currents) a growinggrowing limitation (including for BaBar data quality) limitation (including for BaBar data quality)

Interplay between BaBar radiation-abort strategy, and (primarily)Interplay between BaBar radiation-abort strategy, and (primarily) radiation bursts (spikes/trapped evts) ==> significant source of beam aborts difficult injection (poor injection efficiency, high backgrounds, repeated aborts)

==> major inefficiencies

Backgrounds Backgrounds operational efficiency (’03-’04) operational efficiency (’03-’04)

Radiation-abort strategy

Radiation burstsInjection backgrounds

Beam-beam tails


Backgrounds: long-term projections IBackgrounds: long-term projections I

Experimental background extrapolations

2005 (2009)

Currently based on 2002 bkgd data. An updated characterization will be carried out once PEP-II stabilizes.

BaBar hardware/performance limitations?

2005 (2009)

(see W. Wisniewski’s talk)

extrapolation of ‘traditional’ backgrounds (in present geometry) valid 200x ? * ==> Coulomb still OK? can one extrapolate beam-beam backgrounds – at all? how to take into account evolution of injection losses

any limitations/vulnerabilities in Babar hardware or physics performance? radiation damage? operational limitations (power supplies, trigger/dataflow bandwidth,...) physics performance (tracker occupancy/efficiency/resolution, calorimeter resolution)


SVT elx SVT elx threshold threshold problem problem

??

Projected integrated dose in SVT midplane Projected integrated dose in SVT midplane (Basis: 2002 characterization, no beam-beam tails, no injection improvements)


Extrapolated dose rates in the SVT mid-plane (stable beams)

50 mR/s ~ 10% chip occupancy

Projected SVT data quality Projected SVT data quality (Basis: 2002 characterization, no beam-beam tails)

“BaBar needs to better understand the implications of high beam occupancies”


Projected DCH currents & data-flow dead time Projected DCH currents & data-flow dead time (Basis: 2002 characterization, no beam-beam tails)

remedy under active study


Backgrounds: long-term projections IIBackgrounds: long-term projections II

Beam-beam ?

Lattice mods ? (dynamic aperture)

Beam-gas simulations

• ring: Turtle

• IR Geant4

SR simulations

(an intrinsic part of the new-IR design)

2 themes...2 themes... validate IR upgrade design

make sure that what we install in ’05 does not suffer from built-in flaws...

...at least for those processes we can calculate (SR, beam-gas)

understand / improve backgrounds in present machine

...that are intimately intertwined...that are intimately intertwined validation requires credibility

update “old” simulations to incorporate what we learnt

simulations of present machine/detector configuration better get the ‘right’ answer (when confronted with measurements)...

...if we want to believe predictions for the upgraded IR

improve those backgrounds we canNOT calculate both for today’s and for tomorrow’s sake!


Background analysis & mitigation [BP, LP, TG: some just starting, but too few...]

Background simulations [RB, MB, GC, SM + SLAC (TF/GB)]

Fast monitoring of machine backgrounds PEP-II [MW, C’OG, AP, GDF,...]

injection quality (SVT, EMC: dDose /dIb )

time distribution of injection triggers

data quality: occupancies, dead time,... for the stored beams

in the ‘trickle’ window

more operator-friendly displays (& controls) of radiation inhibits/aborts

BaBar involvement in Accelerator Performance Improvements (I)BaBar involvement in Accelerator Performance Improvements (I)

EMC

L1 trigger rate


Beam dynamics beam-beam simulations [IN (Caltech), YC (Slac ARD)]

beam-beam experiments, monitoring of beam-beam performance

Instrumentation gated camera in LER & HER [D. D., Slac Exptl Grp C + A. Fisher +...]

beam-beam effects (flip-flop, ‘raining buckets’, parasitic crossings)

electron-cloud effects

development of an X-ray beam-size monitor for the LER: SLAC + zone-plate approach: J A (Caltech)

pin hole approach: JK (LBL), HDS

SVTRAD sensor & electronics upgrade [B P et. al. (Stanford); MB/DK et. al. (Irvine) (initiated & funded by BaBar)]

CsI background sensors [JV, Slac Exptl Grp B]

IR geometry, orbit & optics IR orbit monitoring & stability, IP & ring orbit feedbacks

on-line monitoring of IP position PEP-II control system [RB, Slac; GDF, Caltech; ..]

on-line monitoring of luminous spot sizes PEP-II control system

[MW (Slac); GDF (Caltech); MB/GR (Nikhef);...]

BaBar involvement in Accelerator Performance Improvements (II)BaBar involvement in Accelerator Performance Improvements (II)


SummarySummary

BaBarians...BaBarians... ...have (re-started) contributing significantly to the machine

“BaBar-based machine diagnostics “ a growing & important effort

But more help is needed, esp. on medium- & long-term issues

BaBar vulnerabilities BaBar vulnerabilities betterbetter understood understood short term: SVT elx chip, DCH data flow, IFR aging

medium term: SVT (& EMC ?) integrated dose, tracker occupancies, physics systematics

?? implications of lattice mods ( dyn. aperture) for backgrounds?

Most urgent short-term gainsMost urgent short-term gains injection (lack of reproducibility, abort cascades, ++dose, fatigue)

beam-beam tails (more agressive and/or upgraded collimation)

radiation bursts (“dust events”)

Most significant long-term gain potentialMost significant long-term gain potential LER vacuum in last 20 m (?) [tbc by updated bgd characterization]

injection (30-90% of integrated dose in SVT & EMC)


Appendix: radiation bursts (aka ‘dust’ events)Appendix: radiation bursts (aka ‘dust’ events)


Statistical study of trapped event properties (T. Schietinger, 1999)Statistical study of trapped event properties (T. Schietinger, 1999)



SVT diode pattern during trapped eventsSVT diode pattern during trapped events typical, but not universal


An odd sequence of slow radiation bursts (2003)An odd sequence of slow radiation bursts (2003)Diamonds

0

50

100

150

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250

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mR

/s

DIAM_E

DIAM_W

Backward-top diodes (W/E)

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SIG5

HER Betatron collimators (y)

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BL

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ou

nts

PR12_BLHC8072

Inverse HEB lifetime

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0.0015

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0.0035

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0.0045

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Inv

ers

e li

feti

me

(m

in^

-1)

1/tau_H

?

?


An odd sequence of slow radiation bursts (c’td)An odd sequence of slow radiation bursts (c’td)HER Betatron collimators (y)

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7000

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ou

nts

PR12_BLHC8072

Inverse HEB lifetime

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0.0035

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e li

feti

me

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in^

-1)

1/tau_H

?

HER momentum collimator

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PR12_BLHC9082

HER BLMs (incoming S2A)

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BLSC7017


A collection of fast radiation spikes (stored beams)A collection of fast radiation spikes (stored beams)


Geometry of some detectors useful for such studiesGeometry of some detectors useful for such studies

Q1Q2

Q4

Q5

171

192

Amp.20,VSAM 29{outboard Q4)

Amp.19,VSAM 28(inboard Q4)

Amp.18,VSAM 27(next to Q2)

Amp.17,VSAM 26(downstream of Q1)

20

Amp.22,VSAM 31, 3043(Downstream collimator)

Amp.21,VSAM 30(outboard Q5)

IP3

LER

HER

14 4

Amp.23,2-nd VSAM 0, 3054(downstream of a bend)

Amp.24,2-nd VSAM 1, 3075(Upstream collimator)

HER

LER

LER

HER

Q1 Q2

Q4

Q5

10

96 7

Amp.6,VSAM 15(near Q2)



Amp.10,VSAM 19(between Q4&Q5), 7045

8


Amp.5,VSAM 14(upsream of bellows)

IP

51211

Amp.11,VSAM 20(outboard Q5), 7044

Amp.12,VSAM 21(Luminosity chamberdownstream), 7043

13 14

Amp.13,VSAM 22(HER collimatordownstream), 7042

Amp.14,VSAM 23(HER collimatorupstream), 7042

(East)


Radiation bursts: “summary”Radiation bursts: “summary”

Statistical study of trapped event properties (T. Schietinger, 1999)Statistical study of trapped event properties (T. Schietinger, 1999)http://www.slac.stanford.edu/~schieti/background/trapped

SVT diode pattern during trapped eventsSVT diode pattern during trapped eventshttp://www.slac.stanford.edu/~schieti/background/trapped/svt_response.html

A collection of recent slow & fast radiation burstsA collection of recent slow & fast radiation bursts

Some guesses...Some guesses... NEG dust from near IR pumps?

gas ‘bubbles’? (would explain correlation with current increases)

possibly some incorrectly latched fast beam instabilities (RF, TFB ?)

...but certainly no coherent picture nor robust interpretation...but certainly no coherent picture nor robust interpretation


Spare slidesSpare slides


PEP-II Mid-Project EvaluationPEP-II Mid-Project Evaluation

ResourcesEwan Paterson, TDPersis Drell, RDBill Wisniewski, Babar

ResourcesEwan Paterson, TDPersis Drell, RDBill Wisniewski, Babar

Parameters, Parameters, LLdtdt John Seeman, Stan Ecklund

Jonathan Dorfan, Co-ordinator

Lattice/ModelLattice/ModelTor RaubenheimerUli Wienands

Vacuum SystemsVacuum SystemsNadine KuritaScott DeBarger

RF SystemRF SystemRon AkreRay Larsen

Feedback SystemsFeedback SystemsEric ColbyDmitry Teytelman

Reliability/UptimeReliability/UptimeRoger EricksonName #2

Machine/Detector InterfaceMachine/Detector InterfaceWitold KozaneckiGuy Wormser

New IR DesignNew IR DesignMike SullivanName #2

DiagnosticsDiagnosticsMark RossSteve Smith

InjectionInjectionFranz-Josef DeckerName #2

ControlsControlsTom HimelRusty Humphrey

stricly speaking


Fast Abort ChangesFast Abort Changes

Will leave abort settings during stable beams unchangedWill leave abort settings during stable beams unchanged Forgiveness (2 Rad) cannot be increased as that endangers the SVT

Increasing threshold (~1 R/s) could result in running at >1R/s for 10 minutes, which we do not want to try

We can try to change settings during injectionWe can try to change settings during injection There is no immediate danger to the SVT as it is not biased

The increase in dose (a few krad/year) would be regained if we can get rid of 10-20% of the aborts

Suggested change:Suggested change:

Increase forgiveness by factor 3 over stable beams (e.g. 6-8 rads)Increase forgiveness by factor 3 over stable beams (e.g. 6-8 rads)

Set threshold at 2 times stable beams (~2rad/s) instead of 5 timesSet threshold at 2 times stable beams (~2rad/s) instead of 5 times

Would like to have causes of aborts, which still occur be Would like to have causes of aborts, which still occur be identified and logged by operatorsidentified and logged by operators

Brian Petersen, 3

Oct 03


Slow Abort ChangesSlow Abort Changes

We will enable “extend” button for 10-minute timer, but We will enable “extend” button for 10-minute timer, but restrict it to 10 additional minutesrestrict it to 10 additional minutes

We will monitor it for abuse (of course)

Activate 10 minute timer for the diamonds Activate 10 minute timer for the diamonds Suggest to replace BW:MID diode with BW diamond

Use threshold of 75 mrad/s?

Changes can be implemented by next week

Brian Petersen, 3

Oct 03


Possible Longer Term ChangesPossible Longer Term Changes

Should separate “forgiveness” from protection against very Should separate “forgiveness” from protection against very fast spikesfast spikes

Very quickly abort beams on dose rates of 0.1 to 1krad/s

Allow rates of 1-100 Rad/s for a little longer (x2-4?) than today

Requires the SVTRAD1.5

Abort only one beam?Abort only one beam? Not clear that HER and LER always clearly separated during aborts

Gain in integrated dose will be minimal as most aborts would be of the HER

Would require new electronics in IR-2 alcove (previous electronics were done by Mark Petree)

Brian Petersen, 3

Oct 03


MID Radiation Doses Until NowMID Radiation Doses Until Now

Budget is set to reach 4 Mrad by 7/1-2005 (to be lowered?)

FW:MID is consistently overestimated in Run 3


TOP Module Doses until 2009TOP Module Doses until 2009

TOP modules look OK, except if FE:TOP becomes MID module

BW:TOP and FW:TOP doses are probably overestimated

85-90% of the dose is supposed to come from injection


BABAR scorecard todayBABAR scorecard today

TODAYRadiation damage Operation Data Quality

SVT x xDCHDRC fixedEMC - ?IFR x x xTRGDAQSVTRAD x x

X: visible effect with non-zero impact - : visible effect with no impact

? : yet unknown fixed: det upgrade to fix a significant issue

G. Wormser, Bgd Workshop

summary, 24 Sep 03


BABAR scorecard July 2004BABAR scorecard July 2004

July 2004Radiation damage Operation Data Quality

SVT X? xDCH XDRC fixedEMC - ??IFR x X XTRGDAQSVTRAD x improved


summary, 24 Sep 03


BABAR scorecard July 2006BABAR scorecard July 2006

July 2006Radiation damage Operation Data Quality

SVT fixed xxDCH TO BE FIXEDDRC fixedEMC - ???IFR fixed fixed fixedTRGDAQSVTRAD fixed fixed


summary, 24 Sep 03


BABAR scorecard 2009BABAR scorecard 2009

2009Radiation damage Operation Data Quality

SVT X xxxDCH fixedDRC fixedEMC X ????IFR X X XTRG XDAQ XSVTRAD fixed fixed


summary, 24 Sep 03


Architecture of background simulations (1)Architecture of background simulations (1)

Synchrotron RadiationSynchrotron Radiation MAGBENDS / QSRAD: stand-alone programs

SR background calculations: an intrinsic component of IR re-design

shouldn’t these be interfaced to GEANT?

Beam-gasBeam-gas step 1: LP-TURTLE transports particles around 1 ring turn

full model of ring optics (treated as transport line)

start with ‘nominal’ beam at IP

beam-gas scattering randomly around ring (bremsstrahlung or Coulomb scattering) transport ‘secondaries’ (e’, )

simplified model of IR apertures (simple geometry, no showering!)

those particles lost ‘near’ the IP are saved @ scoring plane

input to step 2

step 2: full GEANT simulation of detector + near-IR (+- 8.5 m) see Mario Bondioli’s talk


Architecture of background simulations (2)Architecture of background simulations (2)

Beam-beamBeam-beam full simulation of beam-beam tails impractical

focus on collimation studies optimize collimator placement/relocation (SM)

understand main characteristics of collimator secondaries (HB)

provide guidance for machine experiments

use Turtle machinery

Strategy considerationsStrategy considerations improve/update description of magnetic fields & apertures (TF, GC)

many fundamental features easier to understand at Turtle level first round of IR-upgrade design validation will be done this way (RB)

GEANT-level simulation essential (MB, GB, GC) to benchmark computations against data

to make sure there are no “alligators” hiding in new design

absolute background predictions always suspect even when benchmarked against experiments. However...

...ratios (new design /present machine) much more reliable.


Lost-particle backgroundsLost-particle backgrounds

IP

Normalized to:- uniform pressure profile of 1 nT- 1 A beam current

IP

Coulomb scattering

in Arcs (y-plane)

e- Brems-strahlung

in last 26 m

(x-plane)

Vacuum pipe / mask apertures


The The “Background Zones” “Background Zones” reflect the reflect the combined effectcombined effect of.... of.... beam-line geometry (e.g. bends)

optics at the source and at the detector

aperture restrictions, both distantdistant (good!)(good!) & close-by (bad!)

X (

mm

) Zone 1

X (

mm

)

Zone 2

Zone 3

X (

mm

)

IP

Zone 4

Coulomb scattering

in Arcs

Bremmsstrahlung in field-free region

Bremmsstrahlung

Bremmsstrahlung


Benchmarking of simulations: Benchmarking of simulations: comparing “comparing “predictedpredicted” and ” and measuredmeasured background levels background levels

Radiation patternsRadiation patterns for a given sensor type: independent of absolute calibration

among different sensors: compare fractional derivatives

Absolute background levelsAbsolute background levels sensor calibration!

absolute pressure profile !

Global consistency/sanity checksGlobal consistency/sanity checks operational experience in MCC


Pressure-bump experiment: NEGPressure-bump experiment: NEG heating in BaBar straight heating in BaBar straight

Vacuum gauge reading (nT)

• Create localized P-bumps• NEG heating• DIPS on/off

• Measure response of background monitors

• Compare relative measured & simulated monitor response to validate Monte Carlo

Heated NEG at -8 m

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-BTM

Dose r

ate

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dio

de (

mR

/s)

MCVP7043, scaledDifferent

regions

==>

• diff. patterns• diff. abs. levels

Heated NEG at -60 m

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/s)

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VP7011,scaled

Abort diode signal (mR/s)


Compare measured & predicted dose rates in HER:

• Monte Carlo lost-particle simulation (Turtle + BBSIM) validated by p-bump experiments

• Computed pressure profile in detector straight section (N2-equivalent, not vac.-gauge units!)

• Average ring pressure (from lifetime) for arcs & distant straights

UnderstandingUnderstanding the absolute level of the absolute level of HER backgrounds HER backgrounds (Sep 99)(Sep 99)

BW diode: measured vs. predicted background

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5

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0 0.1 0.2 0.3 0.4 0.5

HEB current (A)

Dose

rate

(m

R/s

)

MC pred

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Abort diodes: msrd/predictedHER background ratio (400 mA)

0.0

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1.0

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OP

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-TO

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-MID

BE

-BTM

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-TO

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-MID

BW

-BTM

Msr

d/p

red r

ati

o

HER pressure model

Zone 1 2 3 4Range (m) 4 to 26 26 to 42 42 to 66 66-2200

P_base (nT) 0.5 0.5 0.5 1.43P_dyn (nT) 2.8 1.2 6.8 3.4

Documents

W. KozaneckiPEP-II MAC Review, 9-11 Oct 03 Machine-Detector Interface Issues Machine Backgrounds, Present & Future BaBar involvement in Accelerator