Transcript Experimental Techniques Where do we come from, where are we going? Bernhard A.

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
Thomas Jefferson National Accelerator Facility
BAM, Gordon Conference 2004
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Topics
• Beams
• Targets
• Detectors
• Electronics + DAQ
• New facilities
I apologize in advance to
everybody whose favorite
topic I have left out.
• Trends
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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
•
deep-inelastic scattering
scaling
•
e+e- collisions + large acceptance coverage
J/Psi (October 1974)
•
polarized beam and target
nucleon spin structure
•
precise data for gN
tests of Chiral PT
•
polarization + Rosenbluth data for Gep/Gmp
importance of 2g effects?
•
investigation of KN final states
penta-quark?
pN
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quarks)
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Experiment Schematics
Data acquisition
and storage
Source
(pol.)
Accelerator
target
(polarized)
Thomas Jefferson National Accelerator Facility
Data conversion
modules
beam
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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
Thomas Jefferson National Accelerator Facility
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MAMI Microtron
3. Stage
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CEBAF
Continuous Electron Beam Accelerator Facility
recirculating
arcs
Properties
Emax
Imax
Pe
beams
5.8 GeV
200mA
85%
3
accelerating
structures
CHL
RF
separators
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Electron Accelerator Beam Quality
Beam Profile in Hall B
Beam Energy Spread in Hall A Line
obtained with dual wire scanner
synchrotron light interference monitor
10nA to Hall B, 100mA to Hall A
continuous non-destructive measurement
dE/E
-5
x 10
4
s = 130mm
2
0
Thomas Jefferson National Accelerator Facility
BAM, Gordon Conference 2004
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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
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?
Thomas Jefferson National Accelerator Facility
BAM, Gordon Conference 2004
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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
modest push for higher polarization
smaller systematic errors
higher current (many mA required for linac-ring collider)
Thomas Jefferson National Accelerator Facility
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Photon Beams
History
bremsstrahlung beams (endpoint, endpoint difference)
tagged bremsstrahlung (first use at Cornell 1953)
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First Use of Tagged Photon Beam
setup
fast (5 nsec)
coincidence
Thomas Jefferson National Accelerator Facility
Hans
Bethe
BAM,
Boyce
GordonMcDaniel
Conference 2004
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First Use of Tagged Photon Beam
setup
fast (5 nsec)
coincidence
Thomas Jefferson National Accelerator Facility
Hans
Bethe
BAM,
Boyce
GordonMcDaniel
Conference 2004
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Photon Beams
History
bremsstrahlung beams (endpoint, endpoint difference)
tagged bremsstrahlung (first use at Cornell 1953)
laser backscattering g + e g + e (benefiting from synchrotron light rings)
Present status
tagged 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)
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Laser Backscattering: GRAAL at ESRF
variable
collimator
ESRF
6 GeV e
cleaning
magnet
tagging
system
interaction
region
Be mirror
laser optics
fixed
collimator
laser intensity,
position, and
polarization
monitoring
laser
Laser hut
Performance
laser energy
3.53 eV
photon energy
(550 – 1470) MeV
resolution
16 MeV (FWHM)
intensity
2.106/sec
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HIgS Photon Source at TUNL
injector
Principle
•
•
use DUKE 1.2 GeV FEL to
produce UV laser light
laser photons backscatter off
subsequent electron bunch
1.2 GeV Ring
Present capabilities
•
mostly <20 MeV operation
due to lifetime considerations
optical klystron
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)
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Future Source of High-Energy Photons?
Method
collide laser light from FEL with
electrons from single-turn light
source
FEL
dump
dump
e-gun
SC linac
Potential
photon energy (with 12 eV laser)
• 2.4 GeV from 5 GeV ring
• 4.8 GeV from 8 GeV ring
single-turn
synchrotron light
source
photon energy resolution <1%
(collimation, no tagging)
flux > 108/sec
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H/D Polarized Targets
Electron beams
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
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Polarized Solid State Target for CLAS
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H/D Polarized Targets
Electron beams
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)
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 10mK
potential advantage: lower dilution due to nuclear component
(first success at LEGS, also in preparation for GRAAL)
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Bonn Frozen Spin Target
Setup for GDH
experiment at
MAMI tagged
photon beam
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Bonn Frozen Spin Target
(GDH Experiment at MAMI)
Improvement of polarization of deuterated butanol during 2003 running period
(based on detailed ESR studies of different materials at U. of Bochum)
Butanol with
titryl radical
(chemically
doped)
Butanol with
porphyrexid
(radiation
doped)
Thomas Jefferson National Accelerator Facility
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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
Hall A 3He target
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=12mA)
• luminosity ~2.1036cm-2s-1
• average polarization 42%
25 Gauss
Latest development:
• optical pumping of Rb/K mixture
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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
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MAMI 3-Spectrometer Setup
A
B
C
configuration
QSDD
D
QSDD
pmax [MeV/c]
665
810
490
DW [msr]
28
5.6
28
Qmin
18
7
18
Dp/p [%]
20
15
25
all magnet coils resistive
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HRS 4GeV/c Spectrometer Pair in Hall A
DW
dp/p
Dp/p
7 msr
10-4
10-1
all magnet coils
super-conducting
detector
hut
target
Q
beamThomas Jefferson National Accelerator Facility
Q
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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 detection
HERMES (HERA)
LEPS (SPring-8)
CLAS (CEBAF)
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LAGRANGE at GRAAL
liquid
hydrogen
target
scintillator barrel
cylindrical wire chambers
photon beam
lead/
scintillator
sandwich
BGO calorimeter
Components
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
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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
•
•
•
TAPS
First experiments
•
•
CB
forward detector
528 BaF2 crystals with veto
counters
particle ID via fast/slow
scintillation light
D+ magnetic moment from
gp ppog
rare h-decays
Thomas Jefferson National Accelerator Facility
CB: prior service at
SPEAR, DORIS, BNL
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Crystal Ball at MAMI
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LEPS at SPring-8
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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)
Trends
number 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
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Data Acquisition (a personal experience)
Tagged photon beam operation at the
Bonn 500 MeV Synchrotron
500 MeV
Synchrotron
20-channel
Internal tagging
system
radiator
magnetic
spectrometer
time
mid 1970’s
duty-cycle
3%
bunch separation
6 nsec
tagged beam intensity
105/sec
magnetic spectrometer
DW=100 msr
data rate
on-line computer
memory (16 bit)
clock speed
1/10 sec
Nova
32kB core
1.5 MHz
Improvement factors expected
How to handle 1000
events per second??
Thomas Jefferson National Accelerator Facility
100% duty-cycle
30
2 nsec bunch separation
4p spectrometer
overall
3
100
10,000
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Development of Raw Data Volume
‘Moore’s law’
for CPU power
, ,
1000000
source: Ian Bird
E691
E665
GByte/year
E769
,
100000
E791
CDF/D0
KTeV
,
10000
E871
BABAR
CMS/ATLAS
,
1000
E831
ALEPH
JLAB
100
1980
STAR/PHENIX
1990
2000
2010
NA48
ZEUS
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New Facilities
HIgS
MAMI Upgrade
CEBAF 12 GeV Upgrade
e-ion Collider
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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
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add Hall D
(and beam line)
126 GeV CEBAF
Properties
Upgrade magnets
and power supplies
Emax
12 GeV
Imax
80mA
beams 3
CHL-2
Upgrade Experimental Equipment
•
•
•
•
Thomas Jefferson National Accelerator Facility
Glue-X detector in new Hall D
MAD spectrometer in Hall A
upgraded CLAS in Hall B
SHMS spectrometer in Hall C
BAM, Gordon Conference 2004
39
Hall D: GlueX Detector
barrel calorimeter
+ central ToF
cylindrical drift chambers
forward drift chambers
lead-glass
calorimeter
tagged
photon beam
SC solenoid
(LASS, MEGA)
forward time-of-flight
Target
vertex
detector
Cerenkov
2 meters
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40
Medium Acceptance Device Spectrometer in Hall A
Properties
DW
Pmax
Dp/p
dp/p
target
Thomas Jefferson National Accelerator Facility
30 msr
7 GeV/c
30%
5.10-3
Technology
2 SC magnets
120cm circular aperture
cosQ+cos2Q windings
6 Tesla max. field
detector
package
BAM, Gordon Conference 2004
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Upgraded CLAS (CLAS++)
Forward Cerenkov
Forward EC
Forward DC
Inner Cerenkov
Central Detector
Preshower EC
Forward TOF
Torus Cold Ring
Coil Calorimeter
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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
Thomas Jefferson National Accelerator Facility
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43
ELIC Electron-Light Ion Collider Layout
IR
IR Solenoid
IR
3- 7 GeV electrons
Snake
30- 150 GeV light ions
Electron
Injector
CEBAF with Energy Recovery
Beam
dump
Beam Dump
from Lia Merminga at EIC Workshop, JLab 03/15/2004
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Future Trends
Experiments: coverage , polarization observables , accuracy
Accelerators: energy , helicity correlated effects , dedicated collider?
Detectors
focusing magnetic spectrometers: energy , acceptance , resolution
large acceptance spectrometers: luminosity
balance between charged and neutrals
cooperation with HEP
Electronics/DAQ
local intelligence
DAQ rates
on-line analysis
Thomas Jefferson National Accelerator Facility
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