Machine-Detector Interface (MDI) report

M. Weaver PEP-II MAC Review, 13-15 Dec 04

Operational issuesOperational issues radiation aborts

radiation-dose and background monitoring

Background characterizationBackground characterization characterization experiments

long-term projections & vulnerabilities

SimulationsSimulations G4 development status

collimation studies

Other background developmentsOther background developments

Machine-Detector Interface (MDI) reportMachine-Detector Interface (MDI) report

Presented by M. Weaver, SLAC


Run-4 radiation-abort historyRun-4 radiation-abort historyB. Petersen

<stable-beam trips> ~ 1.7/day (Sep 03-Jul 04)

<injection trips> ~ 0.6/day, 1-31 Jul 04


Stable-beam aborts per week

0

5

10

15

20

25

30

35

1/1

1/1

5

1/2

9

2/1

2

2/2

6

3/1

1

3/2

5

4/8

4/2

2

5/6

5/2

0

6/3

6/1

7

7/1

7/1

5

7/2

9

Week ending date (2004)

Ra

dia

ion

ab

ort

s/w

ee

k

Rad. signature only

Sympathetic

Total

1/day

Run-4 radiation-abort history Run-4 radiation-abort history (cont’d)

Since 1 March 04

• 172/332 = 52% sympathetic aborts

• <rad. signature-only aborts> ~ 1/day ...but ~ ½ of these are probably sympathetic!

B. Petersen L. Piemontese / S. Foulkes


Run-4 radiation-dose historyRun-4 radiation-dose history

HER trickle starts

HER trickle starts

Outgassing storms

B. Petersen

Vacuum valve ROD

increase probably

instrumental


Injection- & trickle- background historyInjection- & trickle- background history

EMC trigs (always on) LER trickle

EMC trigs (always on) HER trickle

DCH trigs LER trickle

DCH trigs HER trickle

Monitor using injection-gated triggers (1 s x 15 ms)

HER injection-quality monitor

LERLER injection-quality monitor


Stored-beam background historyStored-beam background history

SVT ocp’cy @ = (LEB-sensitive)

20%

DCH current normalized to Jan 04 background data

I DC

H, m

srd

/pre

d

10%

04

DCH ocp’cy

DCH L1 rate

Dead time

HEB sensitive


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 * (pH0 + PH

Dyn * 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)


Background characterization measurementsBackground characterization measurements

Step 1: Step 1: Beam-current scansBeam-current scans single-beam termssingle-beam terms

Data: Jan 04 (bef. therrmal outgassing crisis)


SVT occupancy (FL1 M01-)

EMC cluster multiplicity

Beam-beam term• present in all subdetectors• fluctuations, short - & long-term • parametrization optimistic ?

Step 2: L & beam-beam termsStep 2: L & beam-beam terms

Total occupancy

-HER single beam

- LER single beam


Step 3: Background ParametrizationsStep 3: Background Parametrizations

DCH example: total current & occupancies

Step 4: Background ExtrapolationsStep 4: Background Extrapolations

IDCH =

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


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


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


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.


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

opportunities to monitor the background.


Turtle Simulation : Turtle Simulation : ee+ + ee-- e e++ ee-- BackgroundBackground

32.5

2 1.51

0.5

LER Radiative Bhabhas

-7.5 -5 -2.5 0 2.5 5 7.5

0

10

20

30

-10

-20

-30

m

cm

M. SullivanFeb. 8, 2004API88k3_R5_RADBHA_TOT_7_5M

3.1 G

eV

3.1 G

eV

9 GeV

9 GeV

M. Sullivan

P. Roudeau, A. Stocchi,

W.K. (preliminary

)

109 GeV/s @ L = 1034

- z (m)


EMC default digi map: luminosity

background (N. Barlow)

W

Fwd Bkwdindex

EE

in

dex

32.5

2 1.51

0.5

LER Radiative Bhabhas

-7.5 -5 -2.5 0 2.5 5 7.5

0

10

20

30

-10

-20

-30

m

cm

M. SullivanFeb. 8, 2004API88k3_R5_RADBHA_TOT_7_5M

3.1 G

eV

3.1 G

eV

9 GeV

9 GeV

Electromagnetic shower debris Electromagnetic shower debris or…or…


NeutronNeutronss

J. Va’vra

Measurements appear consistent with Turtle radiative Bhabha simulation +

GDR cross sections. Projected neutron rates may affect detector electronics –

depends upon neutron energy spectrum.


Turtle Level SimulationsTurtle Level Simulations Beam-gas background from the HER (and LER)Beam-gas background from the HER (and LER)

Where do scattered e- hit? Where do scattered e- come from ?

R. Barlow


Determining detector response requires Geant level simulation

Beam line up to Q5 implemented in Geant4 simulation of BaBar detector

Considering re-implementation for robustness but carrying on w/o

Added e-N, -N and neutron transport to physics processes

Detector background analyses integrated for data and simulation alike

First full G4 simulation output of 2004 geometry recently available

Single beam background comparisons look good (normalization?)

Post-2005 configuration (IR upgrade) Turtle not ready

Q2Q4

Q5

B1Q1

Geant4 SimulationsGeant4 Simulations


Z location where particles are lost.

Colors correspond to upper plot.

Starting x, x’ coordinates of

particles lost along the beamline.

x/x

x’/

x;

Z [m]

IPIP

Beam-Beam Collimation Study

Large X-Emittance: Phase Space PlotLarge X-Emittance: Phase Space Plot


+25.2 m from IP

LER

-25.2 m from IP

X [mm]

X [mm]

xx xx [m] [m] xx [2 [2]]

+25 m+25 m -13.6-13.6 54.254.2 0.00.0

-25 m-25 m +13.6+13.6 54.254.2 37.1137.11

Results are based on an older LER deck (’98) with a tune of 0.57 (in x).


Beam-beam collimation study: summaryBeam-beam collimation study: summary

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


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

Outgassing stormsOutgassing storms


Background analysis & mitigation Background analysis & mitigation [BP, MC/TG, NB, JM/JV, RM, LP, WK/GW]

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

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,...]

injection & trickle quality variables: SVT, DCH, EMC

subdetector occupancies: SVT, DCH, EMC, DIRC

BaBar dead time

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

BaBar-based machine diagnosticsBaBar-based machine diagnostics time distribution of injection triggers [LP, BP, ...]

Online centroids & sizes of luminous region using BaBar ,ee [C’OG, BV, AP, IN, MB,...]

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


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

beam-beam experiments, monitoring of beam-beam performance [WK]

, *, z measurements using , ee

InstrumentationInstrumentation Gated camera: now operational in both in LER & HER [DD, Slac Exptl Grp C]

LER interferometer software [AO, Orsay]

Installation of an X-ray beam-size monitor for the LER [Caltech + LBL + SLAC]

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

CsI background sensors , n detectors & shielding [JV, Slac Exptl Grp B]

Forward end Fe shielding wall (may allow better collimation elsewhere)

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


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


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


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


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

Machine-Detector Interface (MDI) report

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