Research Group

Much of the research is done in close collaboration with experienced LEPP and CLASSE staff scientists. The team is very diverse with expertise in many different areas. The nature of the research oftentimes requires an ability to interact in dynamic collaborative environment.

Active and Past Members (students only listed)

Active:

  • Jeremy Perrin (grad)
  • Nathan Froemming (grad)

Past:

  • Joe Calvey (PhD 2013)
  • Jim Shanks (PhD 2013)
  • Michael Ehrlichman (PhD 2013)
  • Richard Helms (PhD 2008)
  • Jeff Smith (PhD 2005)
  • Daniel Fromowitz (PhD 2000)
  • Walter Hartung (PhD 1996)
  • Tom Pelaia (PhD 1994)
  • Joel Graber (PhD 1993)
  • Peter Bagley (PhD 1991)

Active Undergrads:

  • He He (2016)
  • Greg Tabak (2016)
  • Sumner Hearth (2017)

Recent REU:

  • Zoey Warecki (2012)
  • Sarah Woodall (2010)
  • Dan Gonnella (2009)
  • Dan Carmody & Paul Kehayias (2007)
  • Theodor Brasoveanu (2005)

Research in Accelerator and Elementary Particle Physics

For Students:

  • Non-Cornell students who are interested in doing graduate research in accelerator physics are encouraged to apply for admission through the Field of Physics.
  • Individual study with undergrads is typically limited to juniors and seniors with strong physics preparation. A typical course work is likely to include an E&M course (e.g. PHYS 2213 or PHYS 2217), mechanics and special relativity (PHYS 1116, PHYS2216 and/or PHYS3318). Other useful courses would be waves (PHYS2214 or PHYS2218), intermediate or advanced E&M (PHYS 3323 or PHYS 3327), mathematical physics (equivalent to AEP3210 or AEP3220), computational physics (PHYS4480 or AEP4380), and introduction to accelerator physics (PHYS 4456 when offered). Please contact me if you would like to learn about opportunities in my research group.
  • Come to weekly mtgs.
  • Please feel free to contact me to learn more.

Group Mtgs

Group Mtgs:

  • Weekly mtgs discussing CesrTA research. Every Tuesday at 12:00 in Wilson 301. Pizza.
    • Agenda 12/3/2013:
      • Fast Ion physics and measurement plan.
      • Beam position measurement systematics
      • Simulation of sources of emittance dilution
  • Biweekly mtgs discussing g-2- detectors, digitizers, kicker, systematics. Every other Friday at 12:15 in PSB 301. Pizza.
  • Weekly mtgs discussing g-2 beam dynamics. Every Friday at 4:00 in PSB 308.
    • Agenda: 12/6/2013
      • Injection modeling code

Seminars:

  • Check out seminar series featuring accelerator physics and related fields.

Upcoming openings for PhD Students

New positions for PhD students are available in the CesrTA group and the g-2 group. Contact me for additional information.

Research projects

Halo Monitor
Beam halo is the source of an often debilitating backgrounds in experiments at proton colliders like the LHC. It is notoriously difficult to measure since the population in the halo is almost by definition many orders of magnitude smaller than the population of the core. Synchrotron light detectors are typically sensitive to the 1 sigma core of the beam. The usefullness of the higher event rate anticipated with the high luminosity upgrade of the LHC will be limited by halo. We are collaborating with CERN to develop a monitor that will use x-ray detetors with five or more orders of magnitude of dynamic range in order to see the halo in the glare of the beam core. The device will be tested in the CESR where the distribution of particles in an electron bunch is not so different from that of a proton bunch in the LHC.

Wakefields and Impedance

Intra-beam scattering
In high energy electron/positron storage rings, the beam size is limited by single particle effects, that is the equilibrium of radiation damping and excitation. At very low emittance, and therefore very high density beams, intra-beam scattering plays an increasingly important role. We have been able to achieve low enough single particle emittance in CESR to begin to explore the effects of intrabeam scattering on the equilibrium beam size. We are developing instrumentation to allow a simultaneous measurement of the horizontal, vertical, and longitudinal phase space. Given the flexibility of the storage ring to vary energy and lattice parameters, we will have an unprecedented window on IBS and will be able to test the theory.(Ehrlichman)

Fast Ion Instability
In electron storage rings, the residual gas in the vacuum chamber is ionized and oscillate in the potential well of the beam. If the bunches are spaced far apart, then there is time for the ions to dissipate. But if the bunches are closely spaced in a long train, then the ion density can grow from the head of the train to the tail and couple the motion of lead bunches to trailing bunches. The spectrum of the turn by turn and bunch by bunch positon data can in principle included frequencies peculiar to particular ion masses. Dependence of bunch size, or the amplitude of centrode motion on distance from the head of the train, could be a signature of the fast ion instability.

Touschek scattering
Touschek scattering is characterized by the large change in particle energy that may arise from scattering in the transverse plane in a low emittance high density particle beam. Loss of off energy particles limits lifetime. Because CESR can operate at low energy and very low emittance, we are in a position to explore sensitivites and characterize the phenomona. The superconducting RF system allows the possibility of large variations in the accelerating voltage, and bunch length and Touschek lifetime.

Electron cloud (growth of the cloud)
Growth and evolution of the electron cloud depends on many beam parameters including bunch charge, species, spacing, current, energy, and vertical emittance, in addition to details of the environment such as vacuum chamber surface chemistry, surface roughness, quantum efficiency, reflectivity, etc. Retarding field analyzers are used to measure time averaged dependence of cloud density. Shielded pickups can be used to characterize the cloud on the nanosecond time scale. (Calvey)

Electron cloud beam dynamics
The electron cloud focuses the positron beam, couples the head and tail of the positron bunches, and couples one bunch to the next. We observe bunch dependent tune shifts, single bunch emittance growth and single and multibunch instabilities. The existing theory only incompletely characterizes the data, and there is an opportunity to develop theoretical and computational tools to model and interpret the phenomona, and to extend the reach of the measurements.

Low Emittance Tuning
We have developed instrumentation and techniques that permit routine correction of emittance diluting misalignments to less than 10 pm-rad vertical emittance. We continue to investigate the systematic measurement errors that limit our ability to resolve residual dispersion. The minimum achieved to date (at CESR or any other storage ring) is an order of magnitude greater than the theoretical lower limit, the so-called quantum limit. What new phenomena will emerge as we approach that limit? (Shanks)

g-2 beam dynamics
Model the transport of muons through the inflector that brings the particles into the g-2 storage ring central region, past the kicker and then to their ultimate decay to electrons, or loss to scattering. Coherent oscillations of the stored muons is an important systematic that must be minimized in order that we achieve the 0.1 ppm precision that is the goal of the experiment.

Instrumentation

x-ray beam size monitor
Coded apertures for imaging white beams from single bunches. Develop techniques for measuring intra-bunch motion

visible synchrotron light beam size monitor
Develop bunch by bunch electronics for single bunch measurement of height and width. Interferometry and angular distribution of polarized synchrotron radiation for measurement of vertical size of 15 micron bunch.

Time resolving electron cloud detectors
Properties of the surface of the vacuum chamber determine the time development of the electron cloud.

g-2 injection kicker
Cornell has assumed responsibility for designing, building, and testing the fast injection kicker that directs 3.1GeV muons onto the central orbit of the g-2 storage ring. The single turn kicker magnet requires >4000 A in a pulse with 100ns duration and a repitition rate of 100 Hz. We will model the kicker magnetic field and pulser, then prototype and test the new system. We will also develop instrumentation for measuring the magnetic field on the nanosecond time scale.