The Berkeley Lab Laser Accelerator (BELLA) Center offers two laser facilities to LaserNetUS users. The first offers a PW class laser with pulses of up to 40 Joules on target in as little as 30 fs at 1 Hz repetition rates. The second offers two amplifier arrays providing 50 TW class and 10 TW class pulses, respectively, in pulses as short as 40 fs (see BELLA HTW laser below).
The Center’s own research focuses on the development and application of laser-plasma accelerators (LPAs), which may provide user opportunities in use of the generated beams. LPAs produce ultrahigh accelerating fields (1-100 GV/m) and may provide a compact technology for a variety of applications that include accelerators for high energy physics and drivers for high energy photon sources. Electron beams at 0.01-8 GeV, and ion beams at a few MeV have been produced and measured. Femtosecond, keV band betatron radiation is produced from the acceleration process. Quasi-monoenergetic MeV photon beams are produced by Thomson scattering of a laser from the electron beam.
The BELLA Petawatt Laser is a Ti:sapphire CPA laser providing laser pulses at petawatt-level peak power with a repetition rate, unprecedented at that power, of 1 Hz. It was designed, built and installed in collaboration with a commercial vendor (Thales).
The laser consists of a front end system that outputs ~1.4 joules/pulse (uncompressed) at 10 Hz, followed by two final amplifiers that operate at the final 1 Hz repetition rate. The final uncompressed pulse energy is > 65 J. This is sent to a grating-based optical compressor that produces >40 J compressed pulses which can be shorter than 30 femtoseconds, reaching a peak power of ~1 petawatt. The laser is subsequently focused with a long focal length off-axis paraboloid mirror into the target chamber.
The laser is equipped with sophisticated diagnostics and controls. Control systems safely operate and continuously monitor its important parameters from a centrally located control room. A magnetic electron spectrometer using phosphor screens and multiple CCD cameras allows high repetition rate analysis. This is backed up by on-line neutron and gamma ray monitoring. Optical diagnostics monitor the energy, spectrum, and other parameters of the transmitted laser to infer its coupling to the LPA.
The primary activities are focused on the research and development of LPAs at energies expected to reach 10 GeV. This includes controlled production, detailed characterization, and applications of the electron beams.
The laser has been used to produce electron beams up to 8 GeV. It has also been used to produce high charge ion beams, which have been diagnosed using a Thomson parabola spectrometer as well as RCF stacks available on the facility (see e. g. S. Steinke, et al., Phys. Rev. Accel. Beams 23, 021302 (2020)). For details of the laser system see K. Nakamura et al., IEEE J. Quantum Electron. 53, 1200121 (2017).
We are currently implementing a new short focal length beam line where laser pulse will be focused to intensities ≥1021 W/cm2 in a new target chamber for HEDP experiments with LaserNetUS users.
50 TW peak power at up to 5 Hz driving GeV LPAs and MeV photon sources
The BELLA HTW Laser is a Ti:sapphire CPA laser providing laser pulses in the primary arm at 50 TW-level peak power with a repetition rate of 5 Hz. A secondary laser arm provides 10 TW-level peak power at 5 Hz and is available in the same target chamber for multi-beam experiments. It was designed, built and installed by LBNL staff, using a Coherent front end and Thales pump laser. This system does not have a contrast cleaner and as a result has a femtosecond prepulse in the 1e-3 range at several ns range from the main pulse, which can be reduced using Pockels cells or other methods if needed.
The laser consists of a front end system that outputs ~2mJ/pulse (uncompressed) at 1kHz, followed by three final amplifiers that operate at the final 5 Hz repetition rate. The final uncompressed pulse energy is 4 J in the primary arm and 1 J in the secondary arm. These are sent to grating-based optical compressors producing compressed pulses which can be as short as 40 femtoseconds of >2 J and > 0.5 J respectively.
Both lasers are focused by off-axis paraboloid mirrors of 1.1 -1.5 m focal length in a common target chamber which has an experimental breadboard 47” wide by 131” long. The laser is equipped with sophisticated diagnostics and controls. Control systems safely operate and continuously monitor its important parameters from a centrally located control room. A magnetic electron spectrometer using phosphor screens and multiple CCD cameras allows high repetition rate analysis. This is backed up by on-line neutron and gamma ray monitoring. Optical diagnostics can monitor the energy, spectrum, and other parameters of the transmitted laser to infer its coupling to the LPA. The target chamber has numerous ports on the sides, top and bottom, which can be fitted with windows, feedthrough ports, and target delivery systems. Standard target positioners to position a large array of targets. Gas jet targets have been used to date. A large area downstream of the magnetic spectrometer and shielded from the primary target chamber is available for experiments using photon or neutron beams produced.
The primary activities are focused on the research and development of LPAs at GeV-class energies and their use to produce mono-energetic Thomson photon beams at MeV energies. Betatron radiation in the keV band is also produced. X-ray and MeV photon detectors are available including CCD cameras, scintillators, and Compton spectrometers. Collaborative experiments using photon beams can be discussed.
The default configuration has the primary beam focused at 1.5 m focal length and directed towards the magnetic spectrometer. The secondary beam is focused nearly counter-propagating using a 1.1 m focal length. Other configurations can be considered and should be discussed with the facility.
Membership in and support from LaserNet US provides an opportunity to support user experimental time on BELLA Center systems, outside of the normal BELLA Center experimental run program, and allocated through the LaserNetUS proposal process.
All members of an experimental team expecting to be present at the BELLA Center must be registered with LBNL through the LBNL onboarding process and complete all required courses before arriving (some courses are only required for specific activities). The spokesperson for an accepted LaserNetUS proposal (e.g. they who submitted the proposal) will be asked to name a principal investigator (PI) for the experiment. A BELLA Center Scientist Point Of Contact (POC) will be assigned, who will guide the PI through the steps of preparing for their laser time.
|Pulse duration (I FWHM)||30||fs|
|Max energy on target||40||J|
|Shot energy stability||2.5||%||r.m.s.|
|Focal spot at target|
|focal spot FWHM||<10||μm|
|Strehl ratio||Anticipated ~0.9||(construction in progress)|
|Energy containment||Anticipated 75||%||within||10||µm||radius|
|Repetition Rate||1 Hz|
|Pulse duration (I FWHM)||40||fs|
|Max energy on target||2.5||J|
|Shot energy stability||1||%||r.m.s.|
|Focal spot at target|
|focal spot FWHM||20||µm|
|ns scale||10-9||@ 1 ns (pedestal)|
|ps scale||10-6||@ 5 ps|
|Repetition Rate||3.3||Hz||burst mode|