Inverse Compton scattering is a promising method to implement a high brightness, ultra-short, energy tunable X-ray source at accelerator facilities. We have developed an inverse Compton backscattering X-ray source driven by the multi-10 TW laser installed at Daresbury. Hard X-rays, with spectral peaks ranging from 15 to 30 keV, depending on the scattering geometry, will be generated through the interaction of laser pulses with electron bunches delivered by the energy recovery linac machine, initially known as energy recovery linac prototype and subsequently renamed accelerators and lasers in combined experiments. X-ray pulses containing 9 × 10 7 photons per pulse will be created from head-on collisions, with a pulse duration comparable to the incoming electron bunch length. For transverse collisions 8 × 10 6 photons per pulse will be generated, where the laser pulse transit time defines the X-ray pulse duration. The peak spectral brightness is predicted to be ~10 21  photons/(s mm 2  mrad 2  0.1% Δλ/λ).

Inverse Compton backscattering source driven by the multi-10 TW laser installed at Daresbury

The Stanford Linear Collider (SLC) was the first prototype of a new type of accelerator, the electron-positron linear collider. Many years of dedicated effort were required to understand the physics of this new technology and to develop the techniques for maximizing performance. Key issues were emittance dilution, stability, final beam optimization and background control. Precision, non-invasive diagnostics were required to measure and monitor the beams throughout the machine. Beam-based feedback systems were needed to stabilize energy, trajectory, intensity and the final beam size at the interaction point. A variety of new tuning techniques were developed to correct for residual optical or alignment errors. The final focus system underwent a series of refinements in order to deliver sub-micron size beams. It also took many iterations to understand the sources of backgrounds and develop the methods to control them. The benefit from this accumulated experience was seen in the performance of the SLC during its final run in 1997-98. The luminosity increased by a factor of three to 3*10**30 and the 350,000 Z data sample delivered was nearly double that from all previous runs combined.

SLC Final Performance and Lessons

Polarized X-ray pulses at 0.6 A have been generated via head-on collision of a laser pulse from the high-field laser
facility at Daresbury with a 30 MeV electron bunch in the ALICE energy recovery linear accelerator. The angular
distribution of the backscattered X rays was obtained in single-shot using a scintillation screen. The temporal profile of
the X ray yield as a function of the time delay between the laser pulse and electron bunch was measured and agreed well
with that expected from the collision point dependence of the laser-electron beam longitudinal overlap.

First results from the Daresbury Compton backscattering X-ray source (COBALD)

Compton scattering techniques for the measurement of the transverse beam size of particle beams at future linear colliders (FLC) are proposed. At several locations of the beam delivery system (BDS) of the FLC, beam spot sizes ranging from several hundreds to a few micrometers have to be measured. This is necessary to verify beam optics, to obtain the transverse beam emittance, and to achieve the highest possible luminosity. The large demagnification of the beam in the BDS and the high beam power puts extreme conditions on any measuring device. With conventional techniques at their operational limit in FLC scenarios, new methods for the detection of the transverse beam size have to be developed. For this laser based techniques are proposed capable of measuring high power beams with sizes in the micrometer range. In this paper general aspects and critical issues of a generic device are outlined and specific solutions proposed. Plans to install a laser wire experiment at an accelerator test facility are presented.

Proposing a Laser Based Beam Size Monitor for the Future Linear Collider

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Proposing a laser based beam size monitor for the future linear collider

Beam size estimates made using beam-beam deflections are used for optimization of the Stanford Linear Collider (SLC) electron-positron beam sizes. Typical beam sizes and intensities expected for 1996 operations are 2.1 × 0.6 μm (x, y) at 4.0 × 1010 particles per pulse. Conventional profile monitors, such as scanning wires, fail at charge densities well below this. The laser-based profile monitor uses a finely-focused 350-nm wavelength tripled YLF laser pulse that traverses the particle beam path about 29 cm away from the e+/e− IP. Compton scattered photons and degraded e+/e− are detected as the beam is steered across the laser pulse. The laser pulse has a transverse size of 380 nm and a Rayleigh range of about 5 μm.

A laser-based beam profile monitor for the SLC/SLD interaction region

Beam size estimates made using beam-beam deflections are used for optimization of the Stanford Linear Collider (SLC) electron-positron beam sizes. Beam size and intensity goals for 1996 were 2.1 x 0.6 μm (x,y) at 4.0x10 10 particles per pulse. Conventional profile monitors, such as scanning wires, fail at charge densities well below this. Since the beam-beam deflection does not provide single beam information, another method is needed for Interaction Region (IP) beam size optimization. The laser based profile monitor uses a finely focused 349 nm. wavelength , frequency-tripled YLF laser pulse that traverses the particle beam path about 29 cm away from the e+/e- IP. Compton scattered photons and energy degraded e+/e- are detected as the beam is steered across the laser pulse. The laser pulse has a transverse size, ( σ0, ), of 380 nm and a Rayleigh range of about 5 μm. This is adequate for present or planned SLC beams. Design and results are presented.

/pdf/a-high-performance-spot-size-monitor-16nu7m4u7g.pdf

A high performance spot size monitor

Beam size estimates made using beam-beam deflections are used for optimization of the Stanford Linear Collider (SLC) electron-positron beam sizes. Typical beam sizes and intensities expected for 1996 operations are 2.1×0.6 μm (x,y) at 4.0×1010 particles per pulse. Conventional profile monitors, such as scanning wires, fail at charge densities well below this. Since the beam-beam deflection does not provide single beam size information, another method is needed for interaction point (IP) beam size optimization. The laser-based profile monitor uses a finely focused, 350-nm, wavelength-tripled yttrium-lithium-flouride (YLF) laser pulse that traverses the particle beam path about 29 cm away from the e+/e− IP. Compton scattered photons and degraded e+/e− are detected as the beam is steered across the laser pulse. The laser pulse has a transverse size of 380 nm and a Rayleigh range of about 5 μm. This is adequate for present or planned SLC beams. Design and preliminary results will be presented.

W. Colocho

Papers

A laser-based beam profile monitor for the SLC/SLD interaction region

A high performance spot size monitor

A laser-based beam profile monitor for the SLC/SLD interaction region