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

Patent metadata

Field	Value
Publication number	US-10433412-B2
Application number	US-201815894422-A
Country	US
Kind code	B2
Filing date	Feb 12, 2018
Priority date	Aug 19, 2015
Publication date	Oct 1, 2019
Grant date	Oct 1, 2019

Abstract

This disclosure provides systems, methods, and apparatus related to laser plasma accelerators. In one aspect a block of material defines a gas inlet, a chamber in fluid communication with the gas inlet, a throat in fluid communication with the chamber, a channel in fluid communication with the throat, and a gas outlet in fluid communication with the channel. The throat is configured to generate a supersonic flow of a gas when the gas flows through the throat. The channel includes a ramp that is positioned proximate the gas outlet, with 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.

First claim

What is claimed is:

1. 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.

2. The device of claim 1 , wherein the ramp is angled at about 15 degrees to 45 degrees with respect to the direction of the flow of the gas at the gas outlet, and wherein the ramp is angled towards the gas.

3. The device of claim 1 , wherein a distance between the first surface and the second surface is about 300 microns to 1 millimeter.

4. The device of claim 1 , wherein a distance between the third surface and the fourth surface defining the throat is about 20 microns to 100 microns.

5. The device of claim 1 , wherein a distance between the third surface and the fourth surface defining the gas outlet is about 250 microns to 1 millimeter.

6. The device of claim 1 , wherein the block of material comprises an acrylic glass.

7. The device of claim 1 , wherein the ramp is configured to generate an oblique shock wave in a flow of the gas when the gas is flowing through the device.

8. The device of claim 1 , wherein the channel is configured not to generate any shock waves in the gas until the gas flows past the ramp.

9. The device of claim 1 , wherein the device is configured to generate a flow of a gas including a first region having a first gas density and a second region having a second gas density, and wherein the first gas density is about 1.5 to 2.5 times the second gas density.

10. The device of claim 1 , wherein the gas has a velocity of about Mach 2 to Mach 6 at the gas outlet.

11. 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.

12. The apparatus of claim 11 , wherein the laser system comprises a titanium-sapphire laser.

13. The apparatus of claim 11 , wherein the optical fiber comprises a hypocycloid photonic crystal fiber.

14. 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.

15. The method of claim 14 , wherein the gas is selected from a group consisting of hydrogen, helium, neon, argon, krypton, and xenon.

16. The method of claim 14 , wherein a rate of flow of the gas through the device is about 0.5 liter per minute to about 2 liters per minute.

17. The method of claim 14 , wherein the laser pulse has an energy of less than about 100 millijoules, and wherein the laser pulse has a duration of about 12 femtoseconds to 40 femtoseconds.

18. The method of claim 14 , wherein electrons in the pulse of accelerated electrons have energies of about 1 MeV to 10 MeV.

19. The method of claim 14 , wherein the pulse of accelerated electrons has a duration of about 12 femtoseconds to 40 femtoseconds.

Assignees

• Univ California

Inventors

• Mao Hann-Shin
• Leemans Wim
• Bulanov Stepan

Classifications

• A61N2005/1022

  Generators, e.g. X-ray tubes · CPC title

• A61N5/1007

  Arrangements or means for the introduction of sources into the body · CPC title

• H05H1/54 Primary

  Plasma accelerators · CPC title

• A61N2005/1089

  Electrons · CPC title

• A61N5/1001

  using radiation sources introduced into or applied onto the body; brachytherapy · CPC title