Synchroscan streak camera imaging at a 15-MeV photoinjector with emittance exchange

At the Fermilab A0 photoinjector facility, bunch-length measurements of the laser micropulse and the e-beam micropulse have been done in the past with a fast single-sweep module of the Hamamatsu C5680 streak camera with an intrinsic shot-to-shot trigger jitter of 10-20ps. We have upgraded the camera system with the synchroscan module tuned to 81.25MHz to provide synchronous summing capability with less than 1.5ps FWHM trigger jitter and a phase-locked delay box to provide phase stability of ~1ps over 10s of minutes. These steps allowed us to measure both the UV laser pulse train at 263nm and the e-beam via optical transition radiation (OTR). Due to the low electron beam energies and OTR signals, we typically summed over 50 micropulses with 0.25-1nC per micropulse. The phase-locked delay box allowed us to assess chromatic temporal effects and instigated another upgrade to an all-mirror input optics barrel. In addition, we added a slow sweep horizontal deflection plug-in unit to provide dual-sweep capability for the streak camera. We report on a series of measurements made during the commissioning of these upgrades including bunch-length and phase effects using the emittance exchange beamline and simultaneous imaging of a UV drive laser component, OTR, and the 800nm diagnostics laser.Comment: 26 p

Recruiting And Retaining A Diverse Faculty

It is not news that American universities are not well diversified (e.g., Trower 2002, Antonio 2003).  A quick look at your own faculty list will probably corroborate the literature.  Much has been written not only on the need for a diverse faculty, but also the beneficial relationship between a diverse student body and a diverse faculty.  For example, Antonio (2003) suggests that having a diverse student body: Reduces isolation experienced by faculty of color;broadens the range of what is taught and how, and develops collaboration opportunities and sharing of ideas and pedagogies; reduces the possibility of denial of promotion and tenure because of race or ethnicity as the students may become activists; andreduces expectation placed on faculty to handle minority affairs as the university will more likely have formal programs and administration in place.Student diversity and faculty diversity are mutually supportive, and both should be included in your diversity plan.  With that said, the focus will now be on the seemingly more difficult task of recruiting and retaining a diverse faculty.  While a diverse faculty should include females as well as people of color, the focus will be on faculty of color and specifically African-Americans, as that is where universities, in my opinion, tend to do the poorest job

Conversion of a transverse density modulation into a longitudinal phase space modulation using an emittance exchange technique

We report on an experiment to produce a train of sub-picosecond microbunches using a transverse-to-longitudinal emittance exchange technique. The generation of a modulation on the longitudinal phase space is done by converting an initial horizontal modulation produced using a multislits mask. The preliminary experimental data clearly demonstrate the conversion process. To date only the final energy modulation has been measured. However numerical simulations, in qualitative agreement with the measurements, indicate that the conversion process should also introduce a temporal modulation.Comment: 4 pages, 6 figures. Submitted to the proceedings of the Physics and Applications of High-Brightness Electron Beams (HBEB09), Nov. 16-19, 2009, Maui H

The Future of Graduate Education: What Doth Tomorrow Bring?

Future graduate students and graduate education must accept the axiom that personal and professional growth does not exist for a specific and limited period of time. Developing a program or plan for identifying and delivering or acquiring new skills becomes the responsibility and opportunity for graduate programs, students, and alumni alike. Perhaps most importantly, this essay has suggested that graduate education adopt the philosophy of “life-long learning.” To some, both educators and the educated, such a perspective is to be avoided, as it will require continuous change. To others, change is just another word for opportunity

International Expansion Via Acquisition: The Failed Engagement Of Chromalox And Ero

Growth is a common organizational objective that can be achieved via development and/or acquisition. In this case, a US company seeks to achieve growth, both domestically and internationally, by acquiring a technologically related foreign firm. The logic surrounding the planned acquisition was to expand and improve an existing product line domestically, while gaining immediate access to European markets. Targeted toward upper-division undergraduate business majors and/or graduate business students, this case provides an example of how growth via acquisition can fail for all the wrong reasons

Upgrades of beam diagnostics in support of emittance-exchange experiments at the Fermilab A0 photoinjector

The possibility of using electron beam phase space manipulations to support a free-electron laser accelerator design optimization has motivated our research. An on-going program demonstrating the exchange of transverse horizontal and longitudinal emittances at the Fermilab A0 photoinjector has benefited recently from the upgrade of several of the key diagnostics stations. Accurate measurements of these properties upstream and downstream of the exchanger beamline are needed. Improvements in the screen resolution term and reduced impact of the optical system's depth-of-focus by using YAG:Ce single crystals normal to the beam direction will be described. The requirement to measure small energy spreads (<10 keV) in the spectrometer and the exchange process which resulted in bunch lengths less than 500 fs led to other diagnostics performance adjustments and upgrades as well. A longitudinal to transverse exchange example is also reported.Comment: 16 p

Activation mechanisms in sodium-doped Silicon MOSFETs

We have studied the temperature dependence of the conductivity of a silicon MOSFET containing sodium ions in the oxide above 20 K. We find the impurity band resulting from the presence of charges at the silicon-oxide interface is split into a lower and an upper band. We have observed activation of electrons from the upper band to the conduction band edge as well as from the lower to the upper band. A possible explanation implying the presence of Hubbard bands is given.Comment: published in J. Phys. : Condens. Matte