Photo Injector Test Facility Research Articles

Experimental characterization and numerical simulations of the electron source at PITZ

The Photo Injector Test facility at DESY Zeuthen (PITZ) works on the optimization of electron sources for Free Electron Lasers (FELs). The main motivation and challenge of PITZ is the production of electron beams with high charge and small normalized transverse emittance. Recent results of electron beam studies at PITZ are presented in this paper. The experimental characterization of the electron source is discussed together with beam dynamics simulations.

Development of aerogel Cherenkov detectors at Novosibirsk

The development of aerogel Cherenkov counters with the light collection using a wavelength shifter is described. 80 counters of this type are working in the KEDR detector. A project of similar counters for the SND detector based on “heavy” aerogel with n = 1.13 has been developed. Aerogel with a refractive index of 1.006–1.13 and dimensions of blocks up to 200 × 200 × 50 mm 3 is produced by the Novosibirsk group for use in Cherenkov counters of different types. The Novosibirsk group is participating in the development of LHCb RICH as well as a beam diagnostics for a photo-injector test facility at DESY–Zeuthen. Recently we started development of RICH based on focusing aerogel (FARICH) for the endcap of the SuperBaBar. For the first time in the world the focusing aerogel with layers of different refractive indices has been produced.

Secondary electron emission in a photocathode rf gun

During the last decades, photocathode rf guns have been proven to be successful for providing very high quality electron beams required for vacuum ultraviolet and x-ray free-electron lasers. Beam dynamics simulations show that the electron beam quality in a rf gun depends strongly on the beam dynamics in the vicinity of the cathode. Therefore, the injection process plays a significant role in the beam performance. Several codes are available to simulate the beam dynamics in the gun. They are able to track the beam under the influence of external fields and space charge forces, but details of the emission processes are still missing in these simulations. In photocathode rf guns, the electron beams have a high charge density. Especially during emission from the cathode, the electrons have a very low velocity and experience high longitudinal space charge forces counteracting the applied accelerating field. Because of the space charge field, some part of the electrons emitted from the cathode might move backward to the cathode where they can produce secondary electrons. A high electric field in the gun cavity, on the other hand, generates a large amount of dark current. If the field-emitted electrons from the cathode or any other surface inside the cavity hit the cathode, secondary electrons can be produced as well. For a detailed understanding of the electron beam and dark current in a rf gun, simulations including a model of the secondary electron emission are necessary. In this paper, a simple model is discussed with an application to the beam dynamics at high emission phases in rf guns. Detailed simulations have been done in comparison to measurements at the Photo Injector Test Facility at DESY in Zeuthen. The primary electrons which are photoemitted from the cathode and the secondary electrons which are produced by the primaries at the cathode could be clearly distinguished in measurements and simulations.

Silica aerogel radiators for bunch length measurements

Cherenkov radiators based on silica aerogel are used to measure the electron bunch length at the photo injector test facility at DESY Zeuthen (PITZ). The energy range of those electrons is 4–5 MeV. In this paper, the time resolution defined by the usage of aerogel is calculated analytically and Monte Carlo simulations are performed. It is shown that silica aerogel gives the possibility to reach a time resolution of about 0.1 ps for high photon intensities and a time resolution of about 0.02 ps can be obtained for thin silica aerogel radiators.

Characterization of the electron source at the photo injector test facility at DESY Zeuthen

The Photo Injector Test Facility at DESY Zeuthen (PITZ) was built to test and optimize electron sources for Free Electron Lasers and future linear colliders. The focus is on the production of intense electron beams with minimum transverse emittance and short bunch length as required for FEL operation. The experimental setup includes a 1.5 cell L-band gun cavity with coaxial RF coupler, a solenoid for space charge compensation, a laser capable to generate long pulse trains with variable temporal and spatial pulse shape, an UHV photo cathode exchange system, and an extensive diagnostics section. This contribution will give an overview on the facility and will mainly discuss the measurements of the electron beam transverse phase space. This will include measurements of the transverse and longitudinal laser profile, beam charge as a function of RF phase, and transverse emittance as a function of different parameters. The corresponding measurements of momentum and momentum spread as well as the RF commissioning results will be summarized. As a first application of the PITZ electron source it will be installed at the TESLA Test Facility Free Electron Laser at DESY Hamburg in autumn 2003.

Characterization of the electron source at the photo injector test facility at DESY Zeuthen

The Photo Injector Test Facility at DESY Zeuthen (PITZ) was built to test and optimize electron sources for Free Electron Lasers and future linear colliders. The focus is on the production of intense electron beams with minimum transverse emittance and short bunch length as required for FEL operation. The experimental setup includes a 1.5 cell L-band gun cavity with coaxial RF coupler, a solenoid for space charge compensation, a laser capable to generate long pulse trains with variable temporal and spatial pulse shape, an UHV photo cathode exchange system, and an extensive diagnostics section. This contribution will give an overview on the facility and will mainly discuss the measurements of the electron beam transverse phase space. This will include measurements of the transverse and longitudinal laser profile, beam charge as a function of RF phase, and transverse emittance as a function of different parameters. The corresponding measurements of momentum and momentum spread as well as the RF commissioning results will be summarized. As a first application of the PITZ electron source it will be installed at the TESLA Test Facility Free Electron Laser at DESY Hamburg in autumn 2003.

Measurement of the refractive index of silica aerogel in vacuum

The photo injector test facility at DESY Zeuthen (PITZ) uses Cherenkov radiation of electrons inside aerogel to measure the bunch length of an electron beam. To evaluate the results the refractive index of the aerogel has to be precisely known. The aerogel is used either at atmospheric pressure or in vacuum. The pressure dependence of the refractive index of two aerogel samples is investigated in the range between high vacuum (10 −5 mbar) and atmospheric pressure.

First beam measurements at the photo injector test facility at DESY Zeuthen

The Photo Injector Test facility at DESY Zeuthen (PITZ) was built to develop electron sources for the TESLA Test Facility Free Electron Laser and future linear colliders. The main goal is to study the production of minimum transverse emittance beams with short bunch length at medium charge (∼1nC). The facility includes a 1.5 cell L-band cavity with coaxial RF coupler, a solenoid for space charge compensation, a laser capable to generate long pulse trains, an UHV photo cathode exchange system, and different diagnostics tools. Besides an overview of the facility, its main components and their commissioning, this contribution will concentrate on the first measurements at PITZ with photoelectrons. This will include measurements of the transverse and longitudinal laser profile, charge and quantum efficiency, momentum and momentum spread, transverse electron beam profiles at different locations and first results on transverse emittance.