Fermilab, Batavia
INFN/LNF, Frascati (Roma)
Università di Roma II Tor Vergata, Roma
ANL, Argonne
We have previously experimentally observed and modeled the near-field optical diffraction radiation (ODR) generated by a 3-nC micropulse of a 7-GeV electron beam at the Advanced Photon Source (APS). Due to the high gamma of ~14,000, the scaling factor of γλ/2π was about 1.4 mm for 0.628 um radiation. Thus, a standard CCD camera was sufficient for imaging at an impact parameter of 1.25 mm. The extension of this technique to γ 1000 is challenged by the ·1014 reduction in visible light photon production compared to the APS case. We discuss the feasibility of monitoring at a new Fermilab facility a high average current linac beam of 3000 times more charge in a video frame time and with a more sensitive 12- to 16-bit camera. Numerical integrations of our base model show beam size sensitivity for ±20% level changes at 200- and 400-um base beam sizes. We also evaluated impact parameters of 5 σy and 12 σy for both 800-nm and 10-um observation wavelengths. The latter examples are also related to a proposal to apply the technique to an ~ 0.94 TeV proton beam, but there are trades on photon intensity and beam size sensitivity to be considered at such gammas.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
Low cost bunch-by-bunch longitudinal diagnostics is a key issue of modern accelerators. To face up this challenging demand mid-IR compact uncooled PC HgCdTe detectors have been characterized at DAΦNE. These devices were used to monitor the emission of e- bunches. The first experiment allowed to record 2.7 ns long bunches in the e- ring with a FWHM of a single pulse of about 600 ps. To improve diagnostics at DAΦNE an exit port on a bending magnet of the e+ ring has been set-up to monitor the positron bunch structure. The front-end of this port includes an HV chamber hosting a gold-coated plane mirror that collects and deflects the radiation through a ZnSe window. After the window a simple optical layout in air will focus the radiation on IR detectors. The instrumentation will allow comparison in the ns time domain between the two rings and to identify and characterize bunch instabilities. To improve the established performances new faster IR photovoltaic detectors with sub-ns response times are under characterization. In this work we will present the actual status of the 3+L experiment and new measurements obtained with photovoltaic detectors on the e- ring.
