thomas jefferson national accelerator facility bam, gordon conference 2004 1 experimental techniques...

BAM, Gordon Conference 2004 1 Thomas Jefferson National Accelerator Facility

Experimental TechniquesWhere do we come from,

where are we going?

Bernhard A. Mecking

Jefferson Lab

Gordon Conference on Photonuclear ReactionsAugust 1 - 6, 2004


Topics

• Beams

• Targets

• Detectors

• Electronics + DAQ

• New facilities

• Trends

I apologize in advance to everybody whose favorite topic I have left out.


Technical Progress and Discovery

Intimate connection between establishing a new technical capability and a quantum leap in understanding

Generalfield tightly coupled to advances in vacuum and surface technology, RF, electronics and computing, beam dynamics, simulation

Specific Examples• deep-inelastic scattering scaling quarks)

• e+e- collisions + large acceptance coverage J/Psi (October 1974)

• polarized beam and target nucleon spin structure

• precise data for N N tests of Chiral PT

• polarization + Rosenbluth data for Gep/Gm

p importance of 2 effects?

• investigation of KN final states penta-quark?


Experiment Schematics

Acceleratortarget

(polarized)

Source (pol.)

Data conversion modules

Data acquisition and storage

Detector

beam


Electron Accelerators

History

linear accelerators (HEPL Mark III 1 GeV in 1950, SLAC 20 GeV in 1967,

Saclay, MIT, NIKHEF)

synchrotrons (Bonn 0.5 and 2.5 GeV, Daresbury, DESY 6 GeV)

common features: pulsed RF or changing magnetic field, limits duty-cycle and beam quality

Present status

100% duty-cycle operation using • low-gradient warm accelerator structures + many passes (MAMI)

• superconducting accelerator structures + few passes (CEBAF)

Future developments • higher gradients for e+e- colliders (cost, not duty-cycle important)• energy recovery for FEL, synchrotron light sources, electron beam cooling, etc.• own community: MAMI C, CEBAF 12 GeV upgrade

electron-ion collider


MAMI Microtron 3. Stage


CEBAF Continuous Electron Beam Accelerator Facility

acceleratingstructures

CHL

RF separators

Properties Emax 5.8 GeV

Imax 200A

Pe 85%

beams 3

recirculating arcs


E/E x 10-5

Electron Accelerator Beam Quality

Beam Profile in Hall B

obtained with dual wire scanner

10nA to Hall B, 100A to Hall A

Beam Energy Spread in Hall A Line

synchrotron light interference monitor

continuous non-destructive measurement

4

2

0

= 130m


Electron Accelerators

Historylinear accelerators (HEPL Mark III 1 GeV in 1950, SLAC 20 GeV in 1967,

Saclay, MIT, NIKHEF)

synchrotrons (Bonn 0.5 and 2.5 GeV, DESY 6 GeV)

common features: pulsed RF or changing magnetic field, limits duty-cycle and beam quality

Present status

100% duty-cycle operation using • low-gradient warm accelerator structures + many passes (MAMI)

• superconducting accelerator structures + few passes (CEBAF)

Future developments • high gradients for e+e- colliders (cost, not duty-cycle important)

• energy recovery for FEL, synchrotron light sources, electron beam cooling, etc.

• own community: MAMI C, CEBAF 12 GeV upgrade

electron-ion collider?


Polarized Electron Sources

History1977: first parity violation experiment at SLAC (e D e’X, DIS)

• GaAs photocathode, dye laser, Pe~37% (theoretical max. of 50%)• rapid polarization reversal via Pockels cell • experimental asymmetry ~6 .10-5 (syst. errors 10x smaller)

Present statussame technique• strained GaAs or super-lattice, RF pulsed Ti-sapphire laser, Pe~85%• systematic errors < 2 .10-8 (E158 at SLAC) • polarization measurement at ~ 1% level (Moller and Compton scattering)

Future Developmentsmodest push for higher polarizationsmaller systematic errors higher current (many mA required for linac-ring collider)


Photon Beams

Historybremsstrahlung beams (endpoint, endpoint difference)tagged bremsstrahlung (first use at Cornell 1953)


First Use of Tagged Photon Beam

fast (5 nsec) coincidence

setup

Hans Bethe

Boyce McDaniel


Photon Beams

Historybremsstrahlung beams (endpoint, endpoint difference)tagged bremsstrahlung (first use at Cornell 1953)laser backscattering + e + e (benefiting from synchrotron light rings)

Present statustagged bremsstrahlung routine with cw beam (MAMI, ELSA, CEBAF)• photon flux 107 - 8/sec, limited by accidentals or low-energy background

laser backscattering routine (HIGS, LEGS, GRAAL, LEPS@SPring8)• high polarization at endpoint, tagging required, luminosity limited by parasitic operation

Future developments • tagged bremsstrahlung beam has reached full potential• luminosity limitation in laser backscattering may be helped by continuous

injection at full energy (ANL, SPring8)


Laser Backscattering: GRAAL at ESRF

fixed collimator

tagging system interaction

region

variable collimator

cleaning magnet

ESRF 6 GeV e

Laser hut

laser

Performance

laser energy 3.53 eV

photon energy (550 – 1470) MeV

resolution 16 MeV (FWHM)

intensity 2.106/sec

laser intensity, position, and polarization monitoring

Be mirror laser optics


HIS Photon Source at TUNL

Principle• use DUKE 1.2 GeV FEL to

produce UV laser light

• laser photons backscatter off subsequent electron bunch

Present capabilities• mostly <20 MeV operation

due to lifetime considerations

Future capabilities• upgrade underway to allow for full-energy injection• installation of OK-4 optical klystron (capable of producing up to 12 eV, mirrors?) • maximum energy 200 MeV• maximum flux 108/sec• energy definition via collimation (no tagging)

injector

1.2 GeV Ring

optical klystron


dump

Future Source of High-Energy Photons?

Methodcollide laser light from FEL with electrons from single-turn light source

Potentialphoton energy (with 12 eV laser)• 2.4 GeV from 5 GeV ring • 4.8 GeV from 8 GeV ring

photon energy resolution <1%(collimation, no tagging)

flux > 108/sec

SC linac

e-gun

FELdump

single-turn synchrotron light

source


H/D Polarized Targets

Electron beamsdynamically polarized target (NH3, butanol)

polarize free e at high field (~5T) and low T (~1K)use microwave transitions to transfer e polarization to H or D

maximum luminosity L~5.1034cm-2s-1 (for polarized component)

problems: nuclear background, magnet blocking acceptance


Polarized Solid State Target for CLAS


H/D Polarized Targets

Electron beamsElectron beamsdynamically polarized target (NH3, butanol)

polarize free e at high field (~5T) and low T (~1K)use microwave transitions to transfer e polarization to H or D

maximum luminosity L~5.1034cm-2s-1 (for polarized component)

problems: nuclear background, magnet blocking acceptance

Photon beams (frozen spin target)1. same substance, same polarizing technique

but freeze spin at low T (50mK) and lower field (0.5T) small magnet coil (transparent to particles)

2. HD molecule, brute force polarization at 15T and 10mKpotential advantage: lower dilution due to nuclear component(first success at LEGS, also in preparation for GRAAL)


Setup for GDH experiment at MAMI tagged photon beam

Bonn Frozen Spin Target


Bonn Frozen Spin Target (GDH Experiment at MAMI)

Butanol with porphyrexid (radiation doped)

Butanol with titryl radical (chemically doped)

Improvement of polarization of deuterated butanol during 2003 running period (based on detailed ESR studies of different materials at U. of Bochum)


Polarized 3He Targets

Physics interests• few-body structure

• good approximation for polarized free n (Pn=87 % and Pp=2.7 %), requires corrections for nuclear effects

Standard technique:• optical pumping of Rb vapor, followed

by polarization transfer to 3He through spin-exchange collisions

• target polarization measured by EPR/NMR

Performance• 40cm long target (10atm, Ie=12A)• luminosity ~2.1036cm-2s-1

• average polarization 42%

Hall A 3He target

25 Gauss

Latest development:

• optical pumping of Rb/K mixture


Particle Detection: Focusing Magnetic Spectrometers

advantage• high momentum resolution possible

(due to point-to-point imaging from target _> detector)

• detectors far away from target (behind magnetic channel)- insensitive to background- can operate at very high luminosity

disadvantage• coverage in solid angle and momentum range is limited

examples• 3-spectrometer setup at MAMI• Hall A HRS at JLab


MAMI 3-Spectrometer Setup

A B C

configuration QSDD D QSDD

pmax [MeV/c] 665 810 490

msr 28 5.6 28

min 18 7 18

p/p [%] 20 15 25

all magnet coils resistive


msrp/p 10-4

p/p 10-1

HRS 4GeV/c Spectrometer Pair in Hall A

QQ

Q

D

beam

target

detector hut

‘optical bench’

all magnet coils super-conducting


Particle Detection: Large Acceptance Detectors

advantage: large coverage in solid angle and momentum range possible for

- multi-particle final states

- luminosity limited (photon tagging, polarized target)

disadvantage: resolution and luminosity limited, large # of channels ($$)

examples• optimized for photon detection

SASY (BNL LEGS)LAGRANGE (GRAAL)Crystal Barrel (ELSA)Crystal Ball (MAMI)

• optimized for charged particle detectionHERMES (HERA)LEPS (SPring-8)CLAS (CEBAF)


LAGRANGE at GRAAL

Components480 BGO crystals (21Xo) with PMT readout, -coverage: 25o - 155o

wire chambers for charged particle tracking

forward TOF and photon detection in lead/scintillator sandwich detector

liquid hydrogen target

lead/ scintillator sandwich

BGO calorimeter

scintillator barrel

cylindrical wire chambers

photon beam


Crystal Barrel at ELSA

CB: prior service at LEAR


Crystal Ball - TAPS Combination

Crystal Ball• central detector• 672 NaI crystals• 80 MHz FADC electronics

(collaboration with CMS)

TAPS• forward detector• 528 BaF2 crystals with veto

counters• particle ID via fast/slow

scintillation light

First experiments• + magnetic moment from

p po• rare -decays

CB: prior service at

SPEAR, DORIS, BNL

TAPS

CB


Crystal Ball at MAMI


LEPS at SPring-8


CLAS in Maintenance Position

Operating conditions (e-scattering

luminosity 1034cm-2s-1

hadronic rate 106/sec

Moller e rate 109/sec

e-trigger Cer. + calorimeter

event size 5 kBytes

trigger rate 4,000/sec

data transfer rate 20 Mbytes/sec


Electronic Instrumentation

History• 1950’s: modules in crates; lab (CalTech) or proprietary company (EG&G) standards

• 1960’s: NIM standard (mechanical and electrical, no bus specified)

• 1970’s: CAMAC standard (bus system, limited success for industrial control)

• 1978: FASTBUS standard (high channel density, no industrial use)

• 1981: VME standard (flexible, many industrial applications)

Trendsnumber of industrial suppliers going down

reasons:• custom solutions needed for high-density on-detector electronics• large size collaborations (e.g. LHC) have enough expertise• large projects provide financial incentive for detector-specific developments


How to handle 1000 events per second??

Data Acquisition (a personal experience)

Tagged photon beam operation at the Bonn 500 MeV Synchrotron time mid 1970’s

duty-cycle 3%

bunch separation 6 nsec

tagged beam intensity 105/sec

magnetic spectrometer 100 msr

data rate 1/10 sec

on-line computer Novamemory (16 bit) 32kB coreclock speed 1.5 MHz

Improvement factors expected

100% duty-cycle 30

2 nsec bunch separation 3

4 spectrometer 100

overall 10,000

500 MeV Synchrotron

20-channel Internal tagging system

radiator

magnetic spectrometer

B


Development of Raw Data Volume

100

1000

10000

100000

1000000

1980 1990 2000 2010

E691

E665

E769

E791

CDF/D0

KTeV

E871

BABAR

CMS/ATLAS

E831

ALEPH

J LAB

STAR/PHENIX

NA48

ZEUS

source: Ian Bird‘Moore’s law’ for CPU power

GByte/year

,

,

,

,,


New Facilities

HIS

MAMI Upgrade

CEBAF 12 GeV Upgrade

e-ion Collider


MAMI Upgrade Program

1. add double-sided microton HDSM to increase energy to 1.5 GeV

first beam in 2005

2. add experimental equipment • Crystal Ball • Kaon

Spectrometer


6 GeV CEBAF

CHL-2CHL-2

Upgrade magnets Upgrade magnets and power suppliesand power supplies

12 add Hall D (and beam line)

Upgrade Experimental Equipment• Glue-X detector in new Hall D • MAD spectrometer in Hall A• upgraded CLAS in Hall B• SHMS spectrometer in Hall C

Properties Emax 12 GeV

Imax 80A

beams 3


Hall D: GlueX Detector

forward drift chambers

lead-glass calorimeter

forward time-of-flight

Cerenkov

cylindrical drift chambers

Target vertex detector

2 meters

barrel calorimeter + central ToF

SC solenoid (LASS, MEGA)

tagged photon beam


Medium Acceptance Device Spectrometer in Hall A

Properties 30 msrPmax 7

GeV/cp/p 30%p/p 5.10-3

Technology2 SC magnets120cm circular aperturecoscoswindings6 Tesla max. field

HRS

MAD

D+QD+Q

target

support structure

detector package


Upgraded CLAS (CLAS++)

Forward TOF

Preshower EC

Forward ECForward Cerenkov

Forward DC

Inner Cerenkov

Central Detector

Coil CalorimeterTorus Cold Ring


Future Facility: Electron-Ion Collider?

Physics motivation• study processes at high c.m.s energy and low x ~10-(3-4)

• especially gluon distribution functions

Technical challenges• high luminosity (high bunch charge, electron beam cooling)• polarization control for both beams

Technical approaches• eRHIC

add 10 GeV e-ring to 250 GeV RHIC, L~1033cm-2s-1

• ELIC add 30-150 GeV p-ring to 3-7 GeV single-turn CEBAF, L~1033-35cm-2s-1

could also recirculate 5 GeV to get 25 GeV for fixed target experiments


Ion Linac and pre - booster

IR IR

Beam Dump

Snake

CEBAF with Energy Recovery

3- 7 GeV electrons 30- 150 GeV light ions

Solenoid

- booster

IR IR

Beam Dump

Snake


3- 7 GeV electrons 30- 150 GeV light ions

Solenoid

-

IR IR

Beam dump

Snake


3-7 GeV

electrons30-150 GeV light ions

Solenoid

Electron Injector

Electron

cooling

ELIC Electron-Light Ion Collider Layout

from Lia Merminga at EIC Workshop, JLab 03/15/2004

Ion linac and pre-booster


Future Trends

Experiments: coverage , polarization observables , accuracy

Accelerators: energy , helicity correlated effects , dedicated collider?

Detectorsfocusing magnetic spectrometers: energy , acceptance , resolution

large acceptance spectrometers: luminosity balance between charged and neutrals cooperation with HEP

Electronics/DAQlocal intelligence DAQ rateson-line analysis

thomas jefferson national accelerator facility bam, gordon conference 2004 1 experimental techniques...

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