Parity Quality Beam

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PQB Dinosaur.jpg

A significant portion of the experiments performed at Jefferson Lab require a polarized electron beam. A subset of these are parity violation experiments which have exceptionally stringent requirements on the quality of the electron beam. As the sign of the electron beam helicity reverses at the target of the experiment no other measurable quantity of the electron beam may change. This includes the beam intensity, polarization, position, angle, energy or spot size.

To ensure this beam quality, a significant effort occurs at the polarized electron source, where the laser beam and electron photogun combine to produce the intended electron beam. Also significant is the ability to accelerate the beam to high energy while transporting it to the experimental target, all while maintaining a parity quality electron beam (PQB).


Parity Violation

Discussion of parity violation can be found at NIST: The Fall of Parity: [1]


Parity Violation Experiments

  1. JLab Hall A Parity Experiments (HAPPEX, PREX, C-REX, PVDIS): [2]
  2. JLab Hall C G0 Experiment: [3]
  3. JLab Hall C QWeak Experiment: [4]
  4. JLab Hall A Moller Experiment: [5]
  5. Mainz A4 Experiment: [6]
Jlab parity table.jpg


Selected References

  1. Experimental Test of Parity Conservation in Beta Decay. C. S. Wu et al., Phys. Rev. 105 (1957) 1413 media:PhysRev.105.1413.pdf
  2. Parity-Violating Electron Scattering and the Electric and Magnetic Strange Form Factors of the Nucleon. D. S. Armstrong and R. D. McKeown, Annu. Rev. Nucl. Part. 62 (2012) 337 media:annurev-nucl-102010-130419.pdf


Injector PQB Setup

  1. SLAC's polarized electron source laser system and minimization of electron beam helicity correlations for the E-158 parity violation experiment. T. B. Humensky et al., Nucl. Instr. and Meth. A 521 (2004) 261 media:NuclInstrMethA.521.261.pdf
  2. Helicity correlated asymmetries caused by optical imperfections. K. Aulenbacher, Euro. Phys. J. A 32 (2007) 543 media:EuroPhysJA.32.543.pdf


QWeak PQB

Accelerator Meetings


B-Team Presentations


Collaboration Presentations


Other Presentations


Technical Developments

Discussion of technical developments in preparation for the QWeak experiment:

Jefferson Lab injector development for next generation parity violation experiments. J. Grames, J. Hansknect, M. Poelker, R. Suleiman, Hyperfine Interactions 201 (2011) 69 media:HyperfineInter.201.69.pdf


Jlab source PV2.jpg


Two-Wien Slow Helicity Reversal

  • Two Wien Filter Spin Flipper. J. Grames et al., Part. Accel. Conference (PAC’11), New York, NY, (2011) media:tup025.pdf


New Helicity Board

File:Helicity Settings Summary.jpg
  • The pseudo-random 30-bit Shift Register is shown here (change .txt to .C)

New Pockels Cell HV Switch


Electronic Cross-talk & Ground Loop Elimination


G0 PQB

Need to copy from webpage:

  1. G0 Backward Angle Run
  2. JLab Gun Group G0 experiment homepage
  3. LESSONS LEARNED for parity violation experiments at Jefferson Laboratory is an on-going series of meetings between scientists and students from the accelerator and physics division to learn from past experiences and meet new challenges in the field of parity violation experiments.
  4. Quick links to useful slides and talks:
    1. Parity Violation Experiments at CEBAF Beam Specifications (PPT), Matt Poelker, March 4, 2004
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