Shock injector for low-laser energy electron injection in a laser plasma accelerator

An apparatus comprising:

• a device comprising:
• a block of material, the block of material defining:
• a gas inlet,
• a chamber in fluid communication with the gas inlet,
• a throat in fluid communication with the chamber, the throat being configured to generate a supersonic flow of a gas when the gas flows through the throat,
• a channel in fluid communication with the throat, and
• a gas outlet in fluid communication with the channel, the channel including a ramp that is positioned proximate the gas outlet, the ramp being inclined at an angle with respect to a direction of a flow of the gas proximate a surface of the channel prior to the ramp at the gas outlet,
• the chamber, the throat, and the channel being defined by a first, a second, a third, and a fourth surface, the first surface and the second surface being substantially flat surfaces and being substantially parallel to one another, and a distance between a third surface and a fourth surface defining the channel increasing from a region of the channel proximate the throat to a region proximate the gas outlet;
• a laser system configured to generate a laser pulse;
• and
• an optical fiber, the optical fiber being coupled to the laser system and configured to guide the laser pulse, an end of the optical fiber positioned to direct the laser pulse through the gas when the gas is flowing from the gas outlet.

A method comprising:

• providing a device, the device including:
• a block of material, the block of material defining:
• a gas inlet,
• a chamber in fluid communication with the gas inlet,
• a throat in fluid communication with the chamber, the throat being configured to generate a supersonic flow of a gas when the gas flows through the throat,
• a channel in fluid communication with the throat, and
• a gas outlet in fluid communication with the channel, the channel including a ramp that is positioned proximate the gas outlet, and the ramp being inclined at an angle with respect to a direction of the flow of the gas proximate a surface of the channel prior to the ramp at the gas outlet,
• the chamber, the throat, and the channel being defined by a first, a second, a third, and a fourth surface, the first surface and the second surface being substantially flat surfaces and being substantially parallel to one another, a distance between a third surface and a fourth surface defining the channel increasing from a region of the channel proximate the throat to a region proximate the gas outlet;
• generating a flow of the gas using the device, the flow of the gas including a first region having a first gas density and a second region having a second gas density, a transition region between the first region and the second region being an oblique shock wave and having a width of less than about 5 microns, the first gas density being about 1.5 to 2.5 times the second gas density;
• and
• directing a laser pulse to impinge on the gas flow, the laser pulse travelling through the first region and then the second region, the laser pulse generating a pulse of accelerated electrons.