Photon Physics

Michelle Shinn

May 30, 2013

Jefferson Lab User’s Group Meeting

Newport News, VA

This work was supported by U.S. DOE Contract No. DE-AC05-84-ER40150, the Commonwealth of Virginia, Air Force Office of Scientific Research, DOE Basic Energy Sciences, the Office of Naval Research, and the Joint Technology Office.

with Jefferson Lab’s Free-Electron Laser

Outline

• An introduction to Free-Electron Lasers (FELs)

– What makes the JLab FELs unique?

• Exploring the nature of matter with the FEL

– Applications in the THz, IR, UV, & VUV

• Conclusions

The Jefferson Lab Site & Free Electron Laser Facility

The Free-electron laser (FEL)

History of the FELs at JLab• 1989 Two JLab scientists propose using SRF linac technology to drive an

FEL.

• 1991 Hermann Grunder the first Director, recruits hires two scientists to, among other things, build the case for an FEL at JLab.

• 1994 A team is assembled to create and submit a PDR to the DOE to build an FEL that would operate in the UV for industry and science.

• 1995 May - the PDR “Free Electron Lasers for Industry”, for $27M, was submitted to DOE.

• Proposed demonstration of energy recovery at high currents

• Identified applications included: antimicrobial nylon

– Micro-machined metals, ceramics,…

– Processing electronics materials

Energy recovery enables high average power FELs

• Since the amount of power removed from the beam is small the majority of the beam power is available after the lasing interaction.

• Most facilities dump that beam.

– Creates a lot of induced radioactivity

• We set the pathlength such that the electrons re-entering the cryomodule are 180°in phase with the accelerated bunches.

• The used electrons decelerate and their energy is given back to the RF field in the cavities.

– Electrons are dumped at their original injected energy (< 10 MeV)

– No induced radioactivity

• This raises the overall efficiency of FELs, e.g.,

– We only have enough RF power to accelerate 1 mA of beam.

• But operationally, our current limit is that from the photogun’s DC power supply (10 mA in our case).

– Efficiency improves as the ratio of the beam energy to injection energy.

Existing JLab IR/UV Light Source

E = 135 MeV present limitUp to135 pC pulses @ 75 MHz

20 μJ/pulse in (250)–700 nm UV-VIS 120 μJ/pulse in 1-10 μm IR1 μJ/pulse in THz

The first high current ERL14 kW average power

Ultra-fast (150 fs)

Ultra-bright

VUV Light to Lab 1

wavelength (µm) 1.1 1.6 2.8 6.0cw (kW) 2.2 14.6 6.7 8.5

CW Performance

JLab FEL Facility Performance

NSLS-2

NSLS-1

ULS

Courtesy G. Williams - JLab

The JLab Free Electron Laser User Facility

General Purpose

PLD Microfab

THzLab

Dyna-mics

Nano/NASA

Optics/ Materials

Current User Facility has 7 Labs• Lab1 General set-ups and prototypes• Lab 2 Materials studies• Lab 3 THz dynamics and imaging• Lab 3a NASA nanofab• Lab 4 Aerospace LMES• Lab 5 PLD• Lab 6 FEL + lasers for dynamics

studies

Thomas Jefferson National Accelerator Facility

Jefferson Lab – THz Source Physics

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JLab THz source spectrum

Thomas Jefferson National Accelerator Facility

Courtesy M. Klopf - JLab

THz Imaging Schematic

Beamline

Mirror 1 Mirror 2

Mirror 3

Camera 1

THz CameraTHz filter/lens

2 Watts of broadband light into 3” x 3” field.~104 camera elements, so 200 microWatts per pixel.Scattering ~ 0.1%, so 0.2 microWatts per pixel.Noise level, 1 nanoWatt, so S/N is 200 in real time.

Courtesy G. Williams - JLab

Test of Imaging Resolution

Raw Data Processed Data

• Raw THz images are processed to reduce the background and improve contrast

• Current configuration resolved down to the 1mm wide contact pads• Polyethylene lens filtered the thermal IR, but does not image well

Courtesy G. Williams & M. Klopf - JLab

Real-time Imaging - Jefferson Lab & U. of Delaware Team

Mike Klopf, Matthew Coppinger, GPW, James Kolodzey, Nathan Sustersic

fast MCT detector(TEC cooled)

gas cell

MIR beamfrom FTIR

gas delivery andpressure relief

water lines

THz beamfrom accelerator

THz/MIR Double Resonance Experiments (w/ H. Rutt U. Southampton

Courtesy G. Williams & M. Klopf - JLab

We have plans for a 2 Photon Setup in the THz lab

IR/UV photons THz photons

sample chamber

Thomas Jefferson National Accelerator Facility

THz Spectroscopy of surface plasmons

VO2 sample

heater stage

IR H

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THz Beam from FTIR

THz sensor

A. Lukaszew – W&M & G. Scarel – JMU Courtesy M. Klopf - JLab

Applications in the IR

• Since the beginning of our science program in 1998 we had a mixture of basic and applied science users.

– Material processing

• Metal nitriding/amorphization

– carbon & boron nitride nanotubes

– Medical/biophysics

• Differential heating of fatty tissue

• Treatments on the eye

• As with many of our basic science experiments, when doing applied science, the best use for a high average power FEL is to sweep the parameter space in order to optimize a process.

– Then build a table top device to commercialize the process.

Fat and Water have different spectra in the NIR

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The benefits of high power and tunability - differential heating of fatty tissue to treat acne

Rox Anderson, Harvard Medical School - MGH

Logscale

Linscale

Applications for UV photons

• Determination of the “action spectrum” of human skin to UV radiation.

– This will help in understanding how melanoma develops.

• Microfabrication of nano satellites

• Combustion dynamics

• Coherent and collective effects in materials

– Inorganic and organic

Laser Micro-Fabrication

&Engineering

System

UV FEL application - the COSA propulsion module

• Added to rest of package – has flown in space

We can generate coherent harmonics at useful levels• Harmonics are produced through the electron bunching process that creates gain at

the fundamental.

• This bunching has Fourier components at harmonics of the fundamental frequency and in our case extends into the ultraviolet.

• First few harmonics can be many 10’s of watts.

• Odd harmonics are peaked on-axis and can be degrade coating performance.

• Can also be used to do science.

• We performed measurements in the IR Demo

– “Coherent Harmonics in the Super-Radiant Regime from an FEL”, S.V. Benson, J.F. Gubeli, and M.D. Shinn, Proc. PAC 2001

Harmonics on OC Mirrorwhile lasing at 1.6 micron

3rd harmonic4th harmonic

We can transmit the odd harmonics through a hole in the outcoupler

• Since the odd harmonics are peaked on-axis, we can transmit them through an appropriately sized hole in the downstream mirror’s center.

• The even harmonics have no power on axis and the majority of the power is in two lobes some distance away from center.

• The harmonics source is the electron beam size, so if one knows that, one can calculate the mode size on the mirror, and hence, the size the hole should be.

Initial Science with JLab VUV FEL

1. Atom Trap Trace Analysis (ATTA). Lu Zheng-Tian (ANL) & Charles Sukenik (ODU)

- nuclear physics funded

2. Combustion dynamics. David Osborn (Sandia)

- recommended by Eric Rohlfing, BES

3. Electronic structure of correlated materials.Peter Johnson (BNL), Z.-X. Shen (Stanford)

- co-recipients of 2011 Buckley prize

Courtesy G. Williams - JLab

Atom Trap Trace Analysis (ATTA)

PIs - Lu Zheng-Tian – Argonne National LabCharles Sukenik – Old Dominion University

Science – develop Kr dating.

81Kr clock is 229,000 yrs compared to C, which is 5730 yrs

Qualifications – experiment running at Argonne.

Critical application – dating the polar ice-caps.

Why FEL? – high average power can study small volumes of water.

Advantage of the experiment is that it uses FEL direct beam, without need of monochromator. The sample automatically selects the bandwidth it needs.

Implementation - Idea is to bring equipment from Argonne, and collaborate with local university user. Courtesy G. Williams - JLab

Thomas Jefferson National Accelerator Facility

Jefferson Lab FEL and THz Source – envisioned upgrades

proposed additionalbroadband CSR THz source

proposed narrowbandTHz source

Conclusions

• The Jefferson Lab FEL Facility is a unique in it’s high average brightness in the THz, and IR – VUV spectral regions.

– Sub ps-pulses at MHz repetition rates

• With an installation of a rebuilt “F100” cryomodule the linac energy will increase to > 150MeV.

– Will permit lasing further into the UV and extend VUV.

• With the swap of our CEBAF-style cryounit for an improved booster, we could lase in the VUV.

• Addition of a wiggler and optical cavity slightly canted from the UV beamline would allow simultaneous lasing of UV and THz for high E-field 2 color experiments.

A comment from Mr. Jefferson

• “I have always thought that if in the experiments to introduce or communicate new plants, one species in a hundred is found useful and succeeds, the ninety-nine found otherwise are more than paid for.”

Thomas Jefferson

The Jefferson Lab FEL Team

This work supported by the Office of Naval Research, the Joint Technology Office, the Commonwealth of Virginia, the DOE Air Force Research

Laboratory, The US Army Night Vision Lab, and by DOE under contract DE-AC05-060R23177.

April 24, 2009

FEL PerformanceIR FEL UV FEL UV FEL

3rd HarmonicUV FEL

5th Harmonic

Photon energy range of fundamental

0.1 – 1.4 eV, (12 -0.8 microns)

1 – 3.4 eV(1200-360 nm)

3-10.2 eV(410-120 nm)

5-17 eV(250-73 nm)

Photon energy per pulse

100 microJoules 20 microJoules 20 nanoJoules 0.2 nanoJoules

Repetition rate 4.678 – 74.85 MHz 4.678 MHz 4.68 MHz 4.68 MHz

Photon Pulse length (FWHM)

100 fs – 2 ps 100 fs – 2 ps 100 fs – 2 ps 100 fs – 2 ps

Nominal pulse bandwidth

1% .2% .2% .2%

Electron Beam Energy 80 – 140 MeV 80 – 140 MeV 80 – 140 MeV 80 – 140 MeV

Charge per electron bunch

135 picoCoulombs 60 picoCoulombs 60 picoCoulombs 60 picoCoulombs

Projected

from Marvin Cohen, Physics Today, June 2006, page 48.

reductionist approach - electrons - nuclei

Ultrashort light sources enable new thinking about material research

emergence approach, collective excitations - phonons,, magnons - polarons, plasmons (called quasiparticles)

Application: Laser nitriding automobile cylinder liners (grey cast iron)

Treatment: mirror inside cylinder; rotating engine blockin series production, 5 simultaneous excimer lasers

After honing

After laser treatment

J. Lindner, AUDI AG

Reduction of oil consumption (30x)Slide courtesy of P. Schaaf - U. Göttingen

Uses for carbon and boron nitride nanotubes• Carbon nanotubes are hollow rods (like a soda straw) of pure

carbon.

• They have very small diameters – less than a micron across.

– A human hair is 25-180microns across.

• They can be used to build light and strong structures.

• Boron nitride nanotubes are nontoxic to people – lots of uses.

Future Dark Matter experiments at Jefferson Lab

• Based on the null results of the laser-based experiments done around the world, research is turning to other processes.

• One involves a weak coupling of a particle dubbed the A’ (known as a vector boson, or more colloquially, as a dark photon) that combines with a photon to create an electron/positron pair.

• A positron is the antimatter twin to the electron.

• These combine to form two gamma ray photons with an energy of 0.511MeV.

• Our satellites measure copious 0.511MeV photons emanating from the center of the Milky Way.

• Two JLab experiments are being proposed.

• One uses the main accelerator working in the 1-4 GeV range (APEX)

• The other uses the FEL operating in the ~ 0.1 GeV range. (DarkLight)

• Both are exciting because, while it is new research, it is still within the realm of the Standard Model.

JLab research on Dark Matter

• Astronomical observations during the last century produced overwhelming evidence that there is more matter in the Universe than we can detect.

– Observations from microwaves to X-rays, not just in the visible.

• The current value of the matter density of the Universe is 27.2%

• The other 72.8% is something we call Dark Energy

– Responsible for the accelerating expansion of the Universe.

• Of the 27.3%, only about 5% are the baryons that make up you and me.

– The remaining ~ 22% we call Dark Matter.

• Currently, we only detect its presence through gravity.

• We feel pretty certain some subatomic particle is responsible for this matter, and thousands of researchers worldwide are searching for it.

• JLab has conducted two searches and has two more in the planning stages.

Candidate subatomic particles to explain the observations

• Possibilities• There are as yet undetected subatomic particles which are predicted from

theory (The Standard model, or SM)• Axions• Variants of the neutrino

• Subatomic particles that are not predicted by the SM (Extensions to the Standard Model)• Weakly-interacting massive particles (WIMPS)

• Massive compared to the mass of the proton, 938 million electron volts (MeV)

• Weakly-interacting sub-eV particles (WISPS)

• All of these families of particles have the following properties:• Do not interact with the electromagnetic force• Just gravity and the weak nuclear force

We used the FEL to do a WISP search

O.K. Baker 3rd Joint Conf. Patras, Greece

We used the CEBAF to do a WIMPS experiment

• The APEX (A-prime experiment) was run in the Summer of 2010.

• Searched in the range from about 65 to 550 MeV

APEX detectorsExperimental team

Thomas Jefferson National Accelerator Facility

THz/MIR Double Resonance Experiments

Collaboration between JLab THz group and Harvey Rutt (U. of Southampton)Goal – detect and time-resolve the modulation of the vibrational modes from highly excited rotational modes in small gas phase molecules

Method• utilize the high energy THz pulses from JLab FEL accelerator to “spin up” rotational states

in gas phase molecules• high rep. rate of THz pulses (up to 75 MHz) allows for extremely sensitive lock-in

techniques to be employed• CW MIR beam from globar source is modulated by an FTIR spectrometer to enable

spectral measurements and produce the 2nd modulation for the double-resonance technique

• detection of side-bands off of the THz modulation frequency indicate energy exchange between rotational and vibrational modes

• phase of signals contains information about the time constant of the energy exchange process (in phase = prompt/intramolecular, off phase = scattering/intermolecular)

• real-time analysis software has been coded to achieve a -130 dB noise floor through software implemented band pass filters centered at the sideband frequencies of interest

• both beam paths are fully under vacuum and a gas cell has been fabricated to counterpropagate the MIR and THz beam through the gas sample