A radioisotope production apparatus (RI) comprising an electron source arranged to provide an electron beam (E). The electron source comprises an electron injector (10) and an electron accelerator (20). The radioisotope production apparatus (RI) further comprises a target support structure configured to hold a target (30) and a beam splitter (40) arranged to direct the a first portion of the electron beam along a first path towards a first side of the target (30) and to direct a second portion of the electron beam along a second path towards a second side of the target (30).

A method includes accelerating an electron bunch along a direction of propagation to a relativistic energy and partitioning the electron bunch by transmitting the electron bunch through a grating at the relativistic energy. The grating includes a plurality of alternating narrow portions and wide portions. The narrow portions have a first thickness in a direction substantially parallel to the direction of propagation of the electron bunch, and the wide portions have a second thickness in the direction substantially parallel to the direction of propagation of the electron bunch. The second thickness is greater than the first thickness. The method also includes generating a pulse of light using the partitioned electron bunch.

Orbital debris removal (ODR) systems under the present approach may use a ground- or surface-based FEL and mirror system with sufficient power and both spatial and temporal resolution to both locate Category II OD (1 cm to 10 cm diameter) in low Earth orbit (LEO, 160 to 2000 km altitude) and remove these objects from orbit. Locating the Category II OD is performed by having the light beam from an FEL and its beam director scan a volume of space of interest and then observing the light reflected from the OD. Removing the OD may include heating the OD to a sufficiently high temperature to evaporate the OD, changing the orbit of the OD such as to lower the perigee, or both. Megawatt-class MOPA FELs for, inter alia, removing OD, are described.

Orbital debris removal (ODR) systems under the present approach may use a ground- or surface-based FEL and mirror system with sufficient power and both spatial and temporal resolution to both locate Category II OD (1 cm to 10 cm diameter) in low Earth orbit (LEO, 160 to 2000 km altitude) and remove these objects from orbit. Locating the Category II OD is performed by having the light beam from an FEL and its beam director scan a volume of space of interest and then observing the light reflected from the OD. Removing the OD may include heating the OD to a sufficiently high temperature to evaporate the OD, changing the orbit of the OD such as to lower the perigee, or both. Megawatt-class MOPA FELs for, inter alia, removing OD, are described.

An FEL includes a feedback device for feeding back emitted illumination radiation.

A beam-splitting apparatus arranged to receive an input radiation beam and split the input radiation beam into a plurality of output radiation beams. The beam-splitting apparatus comprising a plurality of reflective diffraction gratings arranged to receive a radiation beam and configured to form a diffraction pattern comprising a plurality of diffraction orders, at least some of the reflective diffraction gratings being arranged to receive a 0.sup.th diffraction order formed at another of the reflective diffraction gratings. The reflective diffraction gratings are arranged such that the optical path of each output radiation beam includes no more than one instance of a diffraction order which is not a 0.sup.th diffraction order.

A method includes simulating diffraction in a transmission geometry of relativistic electron bunches from a crystallographic structure of a crystal thereby simulating diffraction of the relativistic electron bunches into a plurality of Bragg peaks. The method includes selecting a range of angles between a direction of propagation of the relativistic electron bunches and a normal direction of crystal including an angle at which a diffraction portion is maximized. The method includes sequentially accelerating a plurality of physical electron bunches to relativistic energies toward a physical crystal having the crystallographic structure and diffracting the plurality of physical electron bunches off the physical crystal at different angles and measuring the diffraction portion into the respective Bragg peak at the different angles. The method includes selecting a final angle based on the measured diffraction portion into the respective Bragg peak at the different angles and generating a pulse of light.

A helical superconducting undulator includes a cylindrical magnetic core through which a bore hole allows the passage of charged particles. A single superconducting wire wraps the magnetic core guided by helical flights and cylindrical protrusions, to create interleaved helical windings on the magnetic core. An electrical current may be supplied to the superconducting wire to generate a periodic helical magnetic field in the bore. The helical superconducting undulator also includes a strong-back enclosure that acts as an epoxy mold during epoxy impregnation, a structural support to ensure straightness of the undulator after epoxy impregnation, and assists in cooling and thermal control of the magnetic core and superconducting wire during device operation.

An FEL includes a feedback device for feeding back emitted illumination radiation.

A method of accelerating charged particles in a plasma and an associated plasma accelerator and electromagnetic radiation source, the method including creating a region of non-uniform electric field within the plasma which propagates through the plasma; using the non-uniform electric field to accelerate a first plurality of charged particles in the direction of propagation of the region of non-uniform electric field; and once the accelerating first plurality of charged particles have propagated part-way through the plasma: adding a second plurality of charged particles to the plasma, such that the second plurality of charged particles propagates through the plasma, the second plurality of charged particles create a local distortion in the non-uniform electric field experienced by the accelerating first plurality of charged particles, and the local distortion in the non-uniform electric field propagates through the plasma with the accelerating first plurality of charged particles; and the method also including using the local distortion in the non-uniform electric field to accelerate the first plurality of charged particles in the direction of propagation of the region of non-uniform electric field.