Slide 1

Report
Improved beam line for Hall A
• layouts, present and proposed
• optics in altered region
• benefits of proposed layout
• costs of proposed layout
• conclusions
layouts – present and proposed
1m of 10cm tube with
H/V corr, 3” BPM, switch
to 2.5cm tube, quad, 2m
fast raster, BPM, H/V
correctors
ep not possible after Moller scattering (per Kees)
4.5m available where ep is shown, not 5m
Optics plots – altered region (combined optics)
O pt iM - M AIN: - O :\opt im\jf bwork \my opt \New _bas e line \ha llA\halla _5 _1 1 ge v_ re org_c omb_
0
0
DISP_X&Y[m]
BETA_X&Y[m]
5
150
Fri Nov 2 0 1 0 :0 2: 28 20 0 9
1 00
BE TA_X
BE TA_Y
DIS P _ Y
1 50
Size_Y[cm]
0
0
Size_X[cm]
0.1
O pt iM - M AIN: - O :\opt im\jf bwork \my opt \New _ba se line \ha llA\halla _5 _1 1 ge v_ re org_c omb
0.1
Fri Nov 2 0 1 0 :0 2: 54 2 00 9
DIS P _ X
1 00
Ax _bet
Ay _bet
Ax _disp
Ay _disp
1 50
Optics plots 2 (combined optics)
O pt iM - M AIN: - O :\opt im\jf bwork \my opt \New _bas e line \ha llA\halla _5 _1 1 ge v_ re org_c omb_ r2
0
PHASE_X&Y
0.5
Fri Nov 2 0 1 0 :0 4: 10 20 0 9
1 40
Q _X
Q _Y
1 50
BPM
BPM
O pt iM - M AIN: - O :\opt im\jfbwork \myopt \New _ ba se line \hallA\halla _ 5_ 11 ge v _reorg_c omb_r2.
Coordinates X&Y[cm] 0.4
Fri Nov 2 0 10 :0 6: 47 2 00 9
PIVOT
0
p
extent
1 16 .5
X
Moller
raster
Y
1 50
TargetR
aster
MOLLER
Target
PIVOT
Smaller spot at target
OptiM - MAIN: - O :\optim \jf bw ork \m yopt \New _ ba se line \hallA\halla _5 _ 11 ge v_ re org_s m all_ r3
0
0
DISP_X&Y[m]
BETA_X&Y[m]
5
150
Thu Dec 03 1 3: 14 :4 6 2 00 9
1 00
BE TA_X
BE TA_Y
DIS P _ Y
1 60
Size_Y[cm]
0
0
Size_X[cm]
0.05
OptiM - MAIN: - O :\optim\jfbwork \myopt \New _ ba se line \hallA\halla _5 _ 11 ge v_ re org_s ma ll_r3
0.05
Thu Dec 03 1 3: 15 :3 9 2 00 9
DIS P _ X
1 00
Ax _bet
Ay _bet
Ax _disp
Ay _disp
Betas (top) and beam envelopes (bottom) with minima 5m upstream of pivot. Is this
better or worse for beam spot size stability give slow 0.05% changes in quads?
1 60
Benefits
•
•
•
•
•
•
•
•
•
fast raster after all quads so it’s always what you set
quads after Compton may be set for target beam size and BPM phase advance
better control of beam size due to new quad locations
more correctors and BPMs to eliminate scraping and improve orbit locks
better control of orbit through raster and eP due to new BPMs and correctors
fewer ion chamber trips
double raster length eases engineering for 11 GeV
4.5m drift before diagnostic girder allows for either eP system or MOLLER
target insertion
high current Moller polarimetry feasible via combined optics
Costs
•
•
•
•
•
•
•
•
•
•
•
•
Existing fast raster system mounted on leg of Compton before the electron detector as
Moller raster. +-250 microns at electron detector, $5K
Single QR or QA-pair inserted between 1C18 A/B harps on “French bench”. $45K
GEANT simulations to determine effects of elements on 1” beam pipe after Moller
spectrometer dipole and the shielding changes needed as a result. We need to keep S/N
up in Moller polarimeter detectors.
ME design ~$100K
Two girder extrusions and two stands, one extending inverted girder ~$20K
Three additional BPMs and electronics ~$36K
S/H cards for new BPMs $30K??
Three additional H/V corrector sets and power supplies ~$24K
New fast raster system $100K??
If eP not retained, yet another BPM/corrector pair in that drift, $20K
1H00 harp omitted. May fit immediately after IBC/IUN/IBC as it’s mounted there now
– I need more accurate dimensions. Can it be moved next to IPM1P03A? This allows
better optics control at the Compton electron-laser interaction point. New vacuum
vessel will be needed for this region as the middle Compton dipoles move up 8 cm.
Add NEG pumps to improve vacuum near electron detector.
quad upgrades not in 12 GeV project: two 20A power supplies
Further work needed
• Layout to pin down locations to centimeters (Accelerator and
Engineering)
• 11 GeV raster design: 40% longer coil and power supply with twice
the voltage, 40% more current. If the pair of coils of the same plane
must be driven in series, four times the voltage and 1.4 times the
current. (TBD)
• Moller polarimeter dipole and detector S/N modeling; shielding design
with BPMs, correctors and rasters where 4” pipe now exists. Primary
beam through Moller dipole – what corrector strength is needed? (Hall
A collaboration)
• Combined optics must be implemented to allow high current Moller
polarimetry. This requires one quad between the Moller dipole and the
fast raster, increasing design problem of the latter. It will also
constrain either beam size or phase advance in 7m before target.
(Physics and Accelerator)
Conclusions (1)
• A rearrangement of the Hall A line is proposed which
removes a severe optics constraint, raster performance
• Beam quality will be improved for all experiments,
especially 11 GeV parity experiments including MOLLER.
• Ion chamber trips will be reduced, improving availability
and reducing irritation in MCC and the other halls
• Cost of order $0.8M: design, procurements, installation
ep system
• The ep system is not functional.
• It is very difficult to steer in the Compton with the ep ion
chambers set to trip at low values.
• Compton optics matching will take several hours and
disrupt the other halls unless one hour mask durations may
be applied to Compton and ep ion chambers during optics
data acquisition using harps.
• Do any of the remaining 6 GeV experiments require the ep
system? Will the system be of any use at higher energy?
• Might the system be easier to repair if removed from the
hall during January 2010? Replace with 10 cm beam tube
for vacuum conductance.
UVa Polarized target chicane
• 2007 design for g2p requires removal of Moller
polarimeter shielding, inverted quad girder, and final
diagnostic girder for vertical chicane. Moller polarimeter
will be non-functional.
• Proposed design has room for vertical chicane after final
correctors, in space designated for ep and final diagnostic
girder. Moller polarimeter intact.
• Space for second fast raster in proposed design may be
occupied by slow raster.
• Tungsten calorimeter can substitute for Unser and second
BCM as on next slide.
Beamline Chicane
EP
Moller
Major Installation
UVA/Jlab 5 T Polarized Target
Upstream Chicane and supports
Slow raster and Basel SEM.
Instrumentation for 50-100 nA beam.
Local beam dump.
Hall A Septa.
Target
center
Chicane Design : Jay Benesch (JLab CASA)
Two upstream Dipoles, one with vertical degree of freedom.
Reuse the dipoles from the HKS experiment.
Utilize open space upstream of target.
Minimal interference with existing beamline equipment
.
layouts – g2p and this proposal
1m of 10cm tube with
H/V corr, 3” BPM, switch
to 2.5cm tube, quad, 2m
fast raster, BPM, H/V
correctors
4.5m available where ep is shown, not 5m
The Experiment
E0(GeV)
µ(deg)
Days
1.1
6
1.0
1.7
6
1.5
2.2
6
1.6
3.3
6
2.9
4.4
6
2.7
4.4
9
6.0
Data Taking 15.7
Qweak has polarization control for g2p @ 2.2, 3.3 and 4.4 GeV
Overhead 8.4
Total Days 24.1
Conclusions (2)
• The ep system should be removed from the hall ASAP.
Repair offline if the collaboration wishes.
• The proposed Hall A line is more compatible with the
vertical chicane needed for the UVa polarized target and
g2p than is the present line.
• If mechanical design begins in January 2010 and labor is
available it should be possible to install the new line and
g2p in the six month 2011 down.
• BTW – I hope you’ve got the He3 needed for the dilution
refrigerator. DHS has exhausted the supply.

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