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In this article, radio frequency (RF) phase modulation (PM) technology is introduced to effectively improve the beam lifetime and study the longitudinal beam dynamics at Hefei Light Source-II (HLS-II) storage ring. In the experiment, an optical streak camera is employed for real-time observation of the longitudinal distribution and the bunch lengthening under the single-bunch operation mode. Simultaneously, the mechanism of island formation and annihilation caused by PM is deeply investigated based on theoretical analysis and preliminary online experimental measurements. The measured results are in good agreement with the theoretical simulation results. The applicable bunch lengthening factor and the optimal beam lifetime improvement factor are obtained as 2.01 and 1.87, respectively, over the range 20.2–20.7 kHz, which is in the vicinity of the synchrotron frequency. In addition, we further analyze and discuss the corresponding relationship between the modulation frequency and other characteristic parameters of HLS-II, such as the beam size, emittance, and energy spread, under PM.

The traveling time of scintillation photons from the ionization track to the photodetector varies from photon to photon. For scintillators used in (time-of-flight) positron emission tomography (TOF-)PET systems the resulting optical transit time-spread can have a significant influence on the timing resolution. Using a femtosecond pulsed diode laser in combination with a fast imaging streak camera we measured this time-spread on the picosecond time scale for both polished and etched Ca co-doped and non co-doped LSO:Ce and LYSO:Ce crystals of $3 \times 3 \times 5 ~\hbox{mm}^3$ , $3 \times 3 \times 10 ~\hbox{mm}^3$ , and $3 \times 3 \times 20 ~\hbox{mm}^3$ in size. Measurements were performed with the crystals wrapped on 5 of their sides in 1 to 4 layers of 0.1 mm thick white reflecting Teflon tape (PTFE). Optical photons can migrate through Teflon tape for some time before they re-enter the crystal. This Teflon time-spread was measured as well. The roughness of the crystal surfaces were determined using a surface profiler. In addition to experiments, the optical transit time-spread was obtained by means of ray-tracing software and compared to experimental data. In addition, an analytical model about optical transit time-spreads was derived.

In the search for scintillators that have a faster response than existing ones, better knowledge on the processes that take place during the first 100 ps of the scintillation process is required. For that one needs detailed information on the intrinsic rise time of a scintillation pulse. However, the observed rise time, also of direct importance to the timing resolution, is strongly affected by the time spread of photons leaving the scintillator. In this work we pioneered the use of a 120 fs Ti-sapphire laser in combination with a streak camera system to measure those photon time spreads with time resolution up to 5 ps. With this setup the photon time spread distributions of scintillator crystals with different size and/or surface treatment were measured. The potential to study the effect of Teflon packaging on this distribution was also investigated.

A table top picosecond pulsed X-ray and laser induced fluorescence spectrometer using two-dimensional photon counting is presented. With this streak camera system it is possible to measure fluorescence events in a wavelength range from 200-850 nm. Measuring results are full time resolved fluorescence spectra with a temporal resolution up to 20 ps after deconvolution. The instrumental response function (IRF) of the system is around 60 ps for laser excitation and 80 ps for X-ray excitation. For a performance test well known inorganic (CsI, CsI:Tl) and organic scintillators (anthracene) as well as rhodamine 6G for laser induced fluorescence are measured and evaluated. The easily manageable system shows satisfying results in agreement with literature values.

The light emission time response of quenched NE111 plastic scintillators has been measured using a streak camera (20 ps resolution) and 100 to 180 ps, 1.06 ?m, laser-produced, pulsed, low energy x-ray excitation. Each light output pulse was obtained by deconvolution from the film data using the x-ray temporal response measured with an x-ray sensitive streak camera (10 ps resolution). Time response parameters are presented for benzophenone and acetophenone, quenching agents which most effectively reduce the decay time of the singlet component. Full width-half-maximums ? 260 ps were observed for NE111 samples quenched with ? 2% benzophenone. Results are given for unquenched samples consisting of different concentrations of butyl-PBD in PVT and for the phosphor ZnO doped with Ga.

A new technique is described for recording ultrahigh-speed movies of transient events. An optical system is used to reduce an instantaneous two-dimensional image to a set of one dimensional projections whose space and time dependence is recorded by a streak tube. A maximum entropy tomography code is then used to reconstruct a frame of the output movie from each time slice of the streak tube image. The results of simulation studies will be presented, along with a discussion of practical considerations building such a system.

The development and operation of a microchannel plate and its use in photoelectric transducers, photoelectric converters, and streak camera and wide band CRT for picoseconds time resolution are reviewed. The uses of microchannel photomultipliers in hodoscopes, Cherenkov detectors, and a new imaging detection system are discussed. (WHK)

Recent experiments indicate that synchronous untriggered multichannel switching in water will permit the development of relatively simple, ultra-low impedance, short pulse, relativistic electron beam (REB) accelerators. These experiments resulted in the delivery of a 1.5 MV, 0.75 MA, 15 ns pulse into a 2 ? line with a current risetime of 2 x 1014 A/sec. The apparatus consisted of a 3 MV Marx generator and a series of three 112 cm wide strip water lines separated by 2 edge-plane water-gap switches. The Marx generator charged the first line in < 400 ns. The first switch then formed 5 or more channels. The second line was charged in 60 ns and broke down with 10 to 25 channels at a mean field of 1.6 MV/cm. The closure time of each spark channel along both switches was measured with a streak camera and showed low jitter. The resulting fast pulse line construction is simpler and should provide considerable cost savings from previous designs. Multiples of these low impedance lines in parallel can be employed to obtain power levels in the 1014 W range for REB fusion studies.

The longitudinal charge distribution of bunches accelerated in the Stanford Linear Collider (SLC) linac will strongly affect the performance of the Collider. Bunch lengths are chosen in a balance between the deleterious effects of longitudinal and transverse wakefields. The former impacts on the beam energy spread whereas the latter is important to the transverse emittance. Two bunch length measurement ports have been installed in the SLC linac: one in the injector region and one after the emittance damping ring to linac reinjection point. These ports utilize a fused quartz Cerenkov radiator in conjunction with an electrooptic streak camera to permit real time monitoring of single s-band buckets with a resolution of several picoseconds. The design of the radiators and light collection optics is discussed with an emphasis on those issues important to high resolution. Experimental results are presented.

The longitudinal structure of electron bunches in the storage ring SPEAR on a single pass was studied with time resolution approx. 10 ps. The measuring instrument used is an image-converter streak camera, a specialized device heretofore used mostly by laser workers. Unexpectedly, under some conditions the charge in a single RF bucket breaks up into two short sub-bunches which seem to rotate about a common center in energy-phase space. No evidence is seen for other, higher-frequency structure on the bunches.

A self-integrating magnetic-loop device having a risetime of less than 175 ps has been developed to monitor the temporal behavior of the electron beam current and position within each 3.3-ns micropulse generated by the PHERMEX rf linear accelerator. Beam current is measured with a 2-GHz bandwidth by combining these loops in a four-port hybrid summer. Another application of these loops uses two 180° hybrids to give 2-GHz time-resolved beam position to an accuracy of 1 mm. These sensors are nonintrusive to the propagating beam and allow ultrafast beam measurements previously restricted to the technique of recording the Cerenkov-light emission from an intercepting Kapton foil using a streak camera.

The beam diagnostic system of the TRISTAN Accumulation Ring consists of beam position monitors, visible radiation monitors, x-ray monitors, tune measurement setup, etc.. Eighty-six position monitors are installed around the ring. For the closed orbit measurement, a superheterodyne circuit is used to pick up the 479-th harmonic of the revolution frequency (795 kHz) out of beam pulse trains. Synchrotron light is observed in the visible region and in the x-ray region. Visible radiation is used in three ways: profile monitoring by TV cameras, beam current measurement and bunch shape observation by a streak camera. In the x-ray channel a multi-wire ionization chamber is used to get a digitized profile of the x-ray source. Stripline pickxps are installed to detect transverse oscillations of e+ and e- bunches. The envelope signal of pulse trains will be sent to an FFT processor for tune number identification. At the same time the signals are amplified and fed back to wideband deflection electrodes for damping of the oscillaitons.

This paper reviews the formalism of maximum entropy beam diagnostic tomography as applied to the Fusion Materials Irradiation Test (FMIT) prototype accelerator. The same formalism has also been used with streak camera data to produce an ultrahigh speed movie of the beam profile of the Experimental Test Accelerator (ETA) at Livermore.