Improved m fel performance with novel resonator
Sponsored Links
This presentation is the property of its rightful owner.
1 / 15

Improved m FEL performance with novel resonator PowerPoint PPT Presentation


  • 79 Views
  • Uploaded on
  • Presentation posted in: General

Improved m FEL performance with novel resonator. J.H. Brownell, A. Bakhtyari, H.L. Andrews, I.J. Owens Department of Physics and Astronomy, Dartmouth College, Hanover, NH USA M.F. Kimmitt Physics Centre, University of Essex, Colchester CO4 3SQ, UK.

Download Presentation

Improved m FEL performance with novel resonator

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Improved mFEL performance with novel resonator

J.H. Brownell,

A. Bakhtyari, H.L. Andrews, I.J. Owens

Department of Physics and Astronomy,

Dartmouth College,

Hanover, NH USA

M.F. Kimmitt

Physics Centre, University of Essex,

Colchester CO4 3SQ, UK

The miniature free electron laser under development at Dartmouth College is a benchtop device designed to produce coherent, tunable radiation over the entire terahertz spectral range.

We will report on a novel resonator design which significantly enhances the output intensity without limiting the tuning range of the device.


The THz Gap


Desirable characteristics

  • Broad, continuous tuning,

  • Stability,

  • Sufficient power,

  • CW (narrowband) and pulsed,

  • Simple and economical operation,

  • Small footprint, portable.


mFEL schematic

SEM

Electron Beam

Polyethylene Window

Detector

THz Radiation

Grating

TPX Lenses

Specimen Chamber


Smith-Purcell effect

“Open” resonator Wide tuning range


Demonstrated tuningMeasured vs. Calculated wavelengths

Measured wavelengths (microns)

Calculated wavelengths (microns)


x

e-Beam

Grating

Coupling constraint

Evanescent field profile

Must optimize net gain.


Gain

Newton’s eq.

Feedback

Maxwell’s eqs.

Loss & SP signal

  • “Closed” resonator:

  • Increases gain by constraining

  • Reduces loss

  • BUT limits tuning!

Try partial closure.


Typical power from a planar grating

Beam: 29 kV, 40 micron waist

Threshold

Beam

Detected power (a.u.)

Beating

Beam current (mA)


Planar Horn

Electron Beam

Mirror surfaces

Planar grating base

Opening angle


Planar Horn powerfor 20, 40, 90, 180 degree opening angles

Beam: 29 kV, 50 micron waist

Opening angle =

Detected power (a.u.)

Beam current (mA)

Conforms to theory.


Grating Horn

Electron Beam

Ruled

surfaces

Opening angle


Grating Horn power vs. planar grating

Beam: 29 kV, 58 micron waist

Detected power (a.u.)

Beam current (mA)


Other Grating Horn configurations(Distinct boundary conditions)

Electron beam

(a)

(b)

Grating tooth depth

(c)

(d)

(e)

(f)


Conclusion

  • Intensity is magnified by Planar Horn, and even more by Grating Horn,

  • Gain is increased by Grating Horn,

  • High spontaneous signal suggests SP-FEL operates in a fundamentally different way with the Grating Horn,

  • Many configurations to test for optimum performance.

Support:Army Research OfficeNational Science Foundation


  • Login