experimental techniques where do we come from, where are we going?

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BAM, Gordon Conference 2004 1 Thomas Jefferson National Accelerator Facility Experimental Techniques Where do we come from, where are we going? Bernhard A. Mecking Jefferson Lab Gordon Conference on Photonuclear Reactions August 1 - 6, 2004

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Experimental Techniques Where do we come from, where are we going?. Bernhard A. Mecking Jefferson Lab. Gordon Conference on Photonuclear Reactions August 1 - 6, 2004. Topics. Beams Targets Detectors Electronics + DAQ New facilities Trends. - PowerPoint PPT Presentation

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Experimental TechniquesExperimental Techniques
where are we going?
August 1 - 6, 2004
Topics
Beams
Targets
Detectors
Trends
I apologize in advance to everybody whose favorite topic I have left out.
Thomas Jefferson National Accelerator Facility
Technical Progress and Discovery
Intimate connection between establishing a new technical capability and a quantum leap in understanding
General
field tightly coupled to advances in vacuum and surface technology, RF, electronics and computing, beam dynamics, simulation
Specific Examples
polarized beam and target nucleon spin structure
precise data for gN pN tests of Chiral PT
polarization + Rosenbluth data for Gep/Gmp importance of 2g effects?
investigation of KN final states penta-quark?
Thomas Jefferson National Accelerator Facility
Experiment Schematics
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
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
accelerating
structures
CHL
dE/E
10nA to Hall B, 100mA to Hall A
Beam Energy Spread in Hall A Line
synchrotron light interference monitor
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, DESY 6 GeV)
common features: pulsed RF or changing magnetic field, limits duty-cycle and beam quality
Present status
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
History
1977: 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 status
same 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 Developments
smaller systematic errors
Thomas Jefferson National Accelerator Facility
Photon Beams
tagged bremsstrahlung (first use at Cornell 1953)
Thomas Jefferson National Accelerator Facility
First Use of Tagged Photon Beam
fast (5 nsec) coincidence
First Use of Tagged Photon Beam
fast (5 nsec) coincidence
Photon Beams
tagged bremsstrahlung (first use at Cornell 1953)
laser backscattering g + e g + e (benefiting from synchrotron light rings)
Present status
photon flux 107 - 8/sec, limited by accidentals or low-energy background
laser backscattering routine (HIGS, LEGS, GRAAL, [email protected])
high polarization at endpoint, tagging required, luminosity limited by parasitic operation
Future developments
luminosity limitation in laser backscattering may be helped by continuous injection at full energy (ANL, SPring8)
Thomas Jefferson National Accelerator Facility
Laser Backscattering: GRAAL at ESRF
fixed collimator
tagging system
interaction region
variable collimator
cleaning magnet
resolution 16 MeV (FWHM)
Be mirror laser optics
Principle
use DUKE 1.2 GeV FEL to produce UV laser light
laser photons backscatter off subsequent electron bunch
Present capabilities
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
injector
dump
Method
collide laser light from FEL with electrons from single-turn light source
Potential
photon energy resolution <1%
H/D Polarized Targets
dynamically 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
Thomas Jefferson National Accelerator Facility
Polarized Solid State Target for CLAS
Thomas Jefferson National Accelerator Facility
H/D Polarized Targets
dynamically 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)
same substance, same polarizing technique
but freeze spin at low T (50mK) and lower field (0.5T)
small magnet coil (transparent to particles)
HD molecule, brute force polarization at 15T and 10mK
potential advantage: lower dilution due to nuclear component
(first success at LEGS, also in preparation for GRAAL)
Thomas Jefferson National Accelerator Facility
Bonn Frozen Spin Target
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)
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
luminosity ~2.1036cm-2s-1
advantage
detectors far away from target (behind magnetic channel)
- insensitive to background
disadvantage
examples
MAMI 3-Spectrometer Setup
HRS 4GeV/c Spectrometer Pair in Hall A
DW 7 msr
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
disadvantage: resolution and luminosity limited, large # of channels ($$)
examples
HERMES (HERA)
LEPS (SPring-8)
CLAS (CEBAF)
LAGRANGE at GRAAL
480 BGO crystals (21Xo) with PMT readout, Q-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
Crystal Barrel at ELSA
Crystal Ball - TAPS Combination
TAPS
First experiments
rare h-decays
TAPS
CB
Crystal Ball at MAMI
LEPS at SPring-8
CLAS in Maintenance Position
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)
Trends
reasons:
large size collaborations (e.g. LHC) have enough expertise
large projects provide financial incentive for detector-specific developments
Thomas Jefferson National Accelerator Facility
Data Acquisition (a personal experience)
How to handle 1000 events per second??
Tagged photon beam operation at the Bonn 500 MeV Synchrotron
time mid 1970’s
data rate 1/10 sec
clock speed 1.5 MHz
4p spectrometer 100
source: Ian Bird
GByte/year
New Facilities
MAMI Upgrade Program
add double-sided microton HDSM to increase energy to 1.5 GeV
first beam in 2005
Upgrade Experimental Equipment
MAD spectrometer in Hall A
upgraded CLAS in Hall B
SHMS spectrometer in Hall C
Properties
12
Hall D: GlueX Detector
Medium Acceptance Device Spectrometer in Hall A
Properties
Upgraded CLAS (CLAS++)
Future Facility: Electron-Ion Collider?
study processes at high c.m.s energy and low x ~10-(3-4)
especially gluon distribution functions
polarization control for both beams
Technical approaches
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
Thomas Jefferson National Accelerator Facility
ELIC Electron-Light Ion Collider Layout
-
Ion linac and pre-booster
Ion Linac and pre
Future Trends
Accelerators: energy , helicity correlated effects , dedicated collider?
Detectors
large acceptance spectrometers: luminosity
cooperation with HEP