Summary: LPC Workshop
June 19 20, 2000
************* Next LPC Meeting is January 18 & 19, 2001 No June Meeting **************
The first phase of funding for the IR upgrade is in hand and work has begun. Prospects for the second phase of funding are very promising and there are positive indications for the UV upgrade as well. We are firmly on the path from the "IR Demo" to the UV/IR FEL we have so long discussed. Details appear in the summary of the January, 2000, LPC meeting summary. Operation is envisioned for Fall 2002, just time enough to get good experiments organized and in place.
The spring run delivered almost 300 hours of usable beam, reflecting the steady improvement in operating knowledge. Results reported include:
m) vs 1 kHz (Ti:Sapph) suggests that plume interactions are not dominant, though they certainly must occur.
- Spectroscopy of H in Si (Budde, Luepke et al.) - progress continues in characterizing H species, presently the first measurement of the Si-H lifetime.
- Pump-probe spectroscopy of proteins (Austin) results similar to the two year long effort at FELIX are being reproduced.
- AMO physics (Sukenik) the effort to generate high harmonics and multiphoton ionization was not successful, evidently because higher micropulse power is needed.
- Pulsed laser deposition (Reilly) for metals, operating conditions could be found that resulted in markedly lower particulate levels than attainable by excimer laser driven PLD.
- PLD and micromachining of polyimide (Kelley) in contrast with all other lasers, on-resonance FEL-driven ablation showed neither thermal nor photochemical degradation of the target.
- Laser drilling of metals (Shinn) comparison of drill-through time at constant pulse width for 0.75 mm- thick stainless steel at 37.5 MHz (FEL, 3.1
Most of the program was devoted to the FELs potential as a tool for novel basic science research. Its fruitful exploitation must rest upon the platform of a basic research program. The path to establishing the program consists of (Williams):
- Build and enhance existing programs
- Establish a program advisory committee to review scientific proposals: Trevor Sears (BNL), Phillipe Guyot-Sionnest (UCal) and Richard Haglund (Vanderbilt)
- Define guidelines for user proposals see the website
- Establish dialogue with DoE/BES leadership
- Develop the scientific case for DoE support of an operating budget for the FEL workshop in October to define the scientific case.
- Enhance the facilities at JLab negotiations are promising to acquire "Helios I" compact synchrotron by donation from IBM
Even without the upgrades, the FEL offers many exciting opportunities for basic and applied research:
- Biological systems (Miller, NSLS/BNL) high intensity and a wide wavelength range provide open the door to microspectroscopic imaging of biologically significant issues such as time-resolved protein folding, stages in apoptosis (programmed cell death) and the role of gelatinase in tumor growth.
- Ultrafast IR Light (Richter, NSLS/BNL) an important tool for basic chemical physics on surfaces
- IR spectroscopy of gaseous ions (Eyler, Florida) - equipping a gas-phase photochemistry chamber with a Fourier-transform ion cyclotron resonance mass spectrometer provides the opportunity to study IR-driven selective photodissociation of trapped ions.
- Pump-probe spectroscopy of condensed matter (Tanner, Florida) after a chosen delay following excitation by a pump pulse, an IR probe pulse is delivered. Wavelength selection determines what process is followed in the solid; MHz operation gives useful signal intensity with non-damaging intensity in reasonable time.
- Ultra-fast laser superheating of solids (El-Sayed Ali, ODU) intense, short-pulse irradiation can produce a melt-like surface layer as much as 60 K below the nominal melting temperature: surface initiated melting.
- Ultra-fast IR/x-ray pump-probe studies (Happek, Georgia) an intense x-ray pulse generated by Thomson backscattering of the IR off the electron beam follow (with a controlled delay) a structure-modifying IR pulse. Many kinds of information beyond simple diffraction are possible.
- UV laser microfabrication for aerospace applications (Helvajian, Aerospace) a high average power, broadly tunable, ps-pulse UV FEL is a critical enabler for affordable manufacture of sub-kilogram satellites which will play key roles in affordable use of space.
Working groups met to address ablation-based processes (PLD and micromachining), metal and surface processing, and bio/medical opportunities. The major outcomes were:
Ablation- Interests and Action Items
- The importance of moving to 1 micron and then to UV cannot be overemphasized
- We are moving toward beam conditioning hardware: items/responsibilities
- Pulse picker/beam switch Gillman (NSU)
- Beam shaper/"top hat" Shinn (JL)
- IR pulse stacker Kelley (JL/CWM)
- Stretcher/compressor lead TBD
- The end station equipment needs upgrades and people
- Permanent lab assignment and steward for PLD chambers (Reilly/Shinn)
- Engineering and emplace micromachining set-up (Kelley/Hamann)
- Ablation fundamentals lead TBD
Metal and Surface Processing Interests
- Virginia Power surface amorphize turbine blades to improve durability
- AK Steel laser descale instead of pickling
- Siemens 200 micron and smaller holes in 75 micron 1 mm thick stainless steel
Bio/Medical opportunities and interests
- Near UV DNA damage action spectra (Sutherland, NSLS/BNL)
- IR spectroscopic microscopy to understand tissue damage mechanisms (Williams, JL)
- Pump/probe to study energy partitioning in proteins (Austin, Princeton)
- Understand IR wavelength effects in surgery of hard and soft tissues (Ernst, Vanderbilt)
- Understand UV wavelength effects in surgery