thomas jefferson national accelerator facility bam, gordon conference 2004 1 experimental techniques...
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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
BAM, Gordon Conference 2004 2 Thomas Jefferson National Accelerator Facility
Topics
• Beams
• Targets
• Detectors
• Electronics + DAQ
• New facilities
• Trends
I apologize in advance to everybody whose favorite topic I have left out.
BAM, Gordon Conference 2004 3 Thomas Jefferson National Accelerator Facility
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?
BAM, Gordon Conference 2004 4 Thomas Jefferson National Accelerator Facility
Experiment Schematics
Acceleratortarget
(polarized)
Source (pol.)
Data conversion modules
Data acquisition and storage
Detector
beam
BAM, Gordon Conference 2004 5 Thomas Jefferson National Accelerator Facility
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
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MAMI Microtron 3. Stage
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CEBAF Continuous Electron Beam Accelerator Facility
acceleratingstructures
CHL
RF separators
Properties Emax 5.8 GeV
Imax 200A
Pe 85%
beams 3
recirculating arcs
BAM, Gordon Conference 2004 8 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 9 Thomas Jefferson National Accelerator Facility
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?
BAM, Gordon Conference 2004 10 Thomas Jefferson National Accelerator Facility
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)
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Photon Beams
Historybremsstrahlung beams (endpoint, endpoint difference)tagged bremsstrahlung (first use at Cornell 1953)
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First Use of Tagged Photon Beam
fast (5 nsec) coincidence
setup
Hans Bethe
Boyce McDaniel
BAM, Gordon Conference 2004 13 Thomas Jefferson National Accelerator Facility
First Use of Tagged Photon Beam
fast (5 nsec) coincidence
setup
Hans Bethe
Boyce McDaniel
BAM, Gordon Conference 2004 14 Thomas Jefferson National Accelerator Facility
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)
BAM, Gordon Conference 2004 15 Thomas Jefferson National Accelerator Facility
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
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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
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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
BAM, Gordon Conference 2004 18 Thomas Jefferson National Accelerator Facility
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
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Polarized Solid State Target for CLAS
BAM, Gordon Conference 2004 20 Thomas Jefferson National Accelerator Facility
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)
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Setup for GDH experiment at MAMI tagged photon beam
Bonn Frozen Spin Target
BAM, Gordon Conference 2004 22 Thomas Jefferson National Accelerator Facility
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)
BAM, Gordon Conference 2004 23 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 24 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 25 Thomas Jefferson National Accelerator Facility
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
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msrp/p 10-4
p/p 10-1
HRS 4GeV/c Spectrometer Pair in Hall A
Q
D
beam
target
detector hut
‘optical bench’
all magnet coils super-conducting
BAM, Gordon Conference 2004 27 Thomas Jefferson National Accelerator Facility
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)
BAM, Gordon Conference 2004 28 Thomas Jefferson National Accelerator Facility
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
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Crystal Barrel at ELSA
CB: prior service at LEAR
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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
BAM, Gordon Conference 2004 33 Thomas Jefferson National Accelerator Facility
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
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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
BAM, Gordon Conference 2004 35 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 36 Thomas Jefferson National Accelerator Facility
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
,
,
,
,,
BAM, Gordon Conference 2004 37 Thomas Jefferson National Accelerator Facility
New Facilities
HIS
MAMI Upgrade
CEBAF 12 GeV Upgrade
e-ion Collider
BAM, Gordon Conference 2004 38 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 39 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 40 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 41 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 42 Thomas Jefferson National Accelerator Facility
Upgraded CLAS (CLAS++)
Forward TOF
Preshower EC
Forward ECForward Cerenkov
Forward DC
Inner Cerenkov
Central Detector
Coil CalorimeterTorus Cold Ring
BAM, Gordon Conference 2004 43 Thomas Jefferson National Accelerator Facility
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
BAM, Gordon Conference 2004 44 Thomas Jefferson National Accelerator Facility
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
CEBAF with Energy Recovery
3- 7 GeV electrons 30- 150 GeV light ions
Solenoid
-
IR IR
Beam dump
Snake
CEBAF with Energy Recovery
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
BAM, Gordon Conference 2004 45 Thomas Jefferson National Accelerator Facility
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