Standard Presentation

1
Polarization at HERA
POL2000 Group
V.Gharibyan
POL2000 Group
Introduction Transverse Polarimeter
(TPOL) Longitudinal Polarimeter (LPOL) Cavity
Project Machine Aspects Summary
PRC session 16 May 2002
2
HERA II
Spin Configuration and Polarimeters
POL2000 Group
PRC session 16 May 2002
3
HERA Compton Polarimeters
Operating Modes and Principles
POL2000 Group
Laser Compton scattering off HERA electrons
LPOL
TPOL
CW Laser - Single Photon
Pulsing Laser - Multiphoton
Flip laser helicity and measure scattered photons
Py 0.59
Pz 0.59
Spatial Asymmetry
Helicity Dependent g Spectra
PRC session 16 May 2002
Statistical Error DP1 per minute _at_ HERA
average currents
4
Transverse Polarimeter
Upgrade Goals
POL2000 Group
Measure bunch by bunch and Reduce systematic error
Improvements _at_ HERA II
Systematics _at_ HERA I
Online h-y gtConverge better Silicon
Frequent Optimization with SLOW Ctr light
calorimetry Optics
Event by event pedestals DAQ
2D fit Analysis
Online h-y Silicon

Sci-Fiber
PRC session 16 May 2002
0.891
Analysis
lt 1 ALL
5
Transverse Polarimeter
Upgraded TPOL
POL2000 Group
New Position sensitive detectors-
Calorimeter
Calorimeter spatial calibration
New DAQ - measure each bunch
polarization
Compton g Beam
UP
Y
DOWN
Preshower
Sci Fiber
SI Strips XY
Calorimeter (100kHz) Energy-Position
Eg EupEdown
PRC session 16 May 2002
h(Eup - Edown)/(Eup Edown)
Silicon (1kHz) - Position
6
Transverse Polarimeter
Routine Operation (3 May 2002) with Ie 3.5mA
POL2000 Group
Online Display
PRC session 16 May 2002
7
Transverse Polarimeter
Calibrations
POL2000 Group
Light Pol. Optimization
Calorimeter Gain matching abs. Energy scale by
Compton edge Controlled per
minutelt0.5 gt Contribution to beam
polarization lt0.1
PRC session 16 May 2002
8
Transverse Polarimeter
Position Calibration
POL2000 Group
Calibrated _at_DESY, CERN test beamsgt new
AnalyzingPowerOld/1.078 (Preshower effect)
_at_ HERA
Compton Single photon Y position by Silicon vs h
Parametrization
PRC session 16 May 2002
1kHz calibration data
Input for Offline P extraction
9
Transverse Polarimeter
New Offline Analysis
POL2000 Group
Fitted Energy Slices
Fit to MC Rise-Time
2D fit
Variable Analyzing Power
PRC session 16 May 2002
10
Longitudinal Polarimeter
POL2000 Group
No major changes

• Has now two calorimeters which may be used
  alternatively
• Crystal and Sampling with Scn. Fibers XY array
  in front.

• DAQ and SLOW control Software transported to
  faster computers.

• Online and Offline data are stored in HERA
  centralized database
• (similar to TPOL format) available to H1 and
  Zeus.

• Ready for polarization measurements.

Achieved fractional systematic uncertainty
1.6. Nucl.Instrum.Meth.A479334-348
,2002
PRC session 16 May 2002
Upgrading to Cavity Polarimeter in progress.
11
Cavity Polarimeter
Goals for LPOL upgrade
POL2000 Group

• Reduction of systematics (lt1)
• Single photon mode
• Absolute scale calibration using Compton Edge
• and Asymmetry 0 crossing.
• Increase statistics
• High laser power (cw)
• Large stat. Þ Fast measurement Þ
• Fast optimisation of harmonic bumps Þ
• Higher polarisation
• Single bunch polarization error 1 per min

10MHz operating mode Simulation
Events
k1.165eV P0.5 ltng gt/bunch1
S -1
S1
PRC session 16 May 2002
Eg GeV
LPOL measurement in a few photon mode
12
Cavity Polarimeter
Prototype Test Cavity
POL2000 Group
Test Cavity
Final Cavity
Bellows
Mirror
Pumps
Mirror
Bellows
BeamPipe
Laser
Procedure I. Open loop ramp
modulation II. Closed loop ramp Stopped
servo active
V
Achievements
PRC session 16 May 2002
Polarisation Controled at the 0.1 level
Resonance
Dn75MHz
t(scope)/s
13
Cavity Polarimeter
Status and Timelines
POL2000 Group

• Slow control procedure (Optics) almost done
• Mechanics of Final Cavity
• In fabrication since feb. 2002,
• at Orsay during June 2002
• Then test of the whole setup at Orsay
• Calorimeter DAQ system
• Under development

PRC session 16 May 2002
Cavity installation at HERA tunnel Machine long
shutdown _at_ end 2002
14
Polarization
Machine Aspects
POL2000 Group
New Spin Rotators for H1 and Zeus gt less
polarization by 5 estimate for 0.7mm
orbit flatness No anti-Solenoids gt new
compensation scheme still to be
demonstrated Orbit Flatness Control 1.2
0.7mm (RMS) will require implementation of
Beam Based Alignment Harmonic Bump Control
Complex Amplitudes 4 8 16

PRC session 16 May 2002
Expected Average Polarization 55 (Hera I) 50
(HERA II)
15
Summary
POL2000 Group

• TPOL
• sucessfully upgraded
• measures bunch by bunch polarization
• new Silicon and Fiber detectors providing
• data to reduce systematic uncertainities
• ongoing analysis to prove sub percent
• precision.
• LPOL
• ready for polarization measurement
• Cavity upgrade
• well advanced tests with full-scale prototype
• in Paris
• expect to be ready for installation at HERA
• at the end of 2002.

PRC session 16 May 2002