Abstract:
This miniature neutron generator is for active detection of highly enriched uranium using a movable detection system. It is a small size, lightweight, low power consumption neutron generator with ease of operation and maintenance. The detector is based on a simplified ion source and ion transport system.

Description:
STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0001]    None. 
       REFERENCE TO A MICROFICHE APPENDIX 
       [0002]    None. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    This invention relates to the use of a miniature neutron generator for active detection of highly enriched uranium (“HEU”) with movable detection systems. 
         [0005]    2. Description of the Related Art 
         [0006]    One of the most challenging problems in Homeland Security is the detection technique for mass destruction and other contraband. This invention is for a promising technique to detect nuclear materials and in particular weapon-usable materials like HEU and Weapon Grade Plutonium (“WGPu”). 
         [0007]    For active detection of HEU with movable detection systems, small size, lightweight neutron generators and detectors are necessary. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    This miniature neutron generator is for active detection of HEU using a movable detection system. It is a small, lightweight, low power consumption neutron generator with ease of operation and maintenance. The detector is based on a simplified ion source and ion transport system. 
         [0009]    In one aspect, the invention provides a neutron generator that includes a Deuterium gas filled chamber, a high voltage power supply, a field ionization ion source, at least one of a carbon nano-tube, nano-rod or multi-pin tungsten anode and a cathode; 
         [0010]    In another aspect of the invention, a neutron generator is provided that comprises a Deuterium gas filled chamber, a high voltage power supply of 125-150 kV, an ionization source comprising tungsten tips, an anode and a Tritium loaded Titanium thick target, wherein the generator weighs less than 10 kilograms; 
         [0011]    In a further aspect of the invention, a method of detecting highly enriched Uranium associated with a target is provided that includes generating a field ionization of Deuterium by high voltage electric field, providing an ion current, accelerating the ions to hit the target to generate a Deuterium-Tritium reaction and collecting and analyzing the data. 
         [0012]    In yet a further aspect of the invention, a method of detecting highly enriched Uranium associated with a target is provided that comprises generating a high voltage electric field using at least one of carbon nano-tube, nano-rod or multi-pin tungsten anode, providing an ion current using a field ionization source, accelerating the ion current such that the ion current hits the target to generate Deuterium-Tritium neutrons, wherein the ion current is accelerated up to 125-150 kV and collecting and analyzing the data. 
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       [0013]      FIG. 1 . is a schematic of the small neutron generator of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    In this invention, a miniature neutron generator is developed for the neutron yield of 10 9  n/second. The ion source of this neutron generator is a field-ionization ion source. An anode of carbon nano-tubes (“CNT”) or nanorods (“NR”) or metal multi-tips is used for ion beam production up to a mili-Amp or more in a Deuterium gas-filled chamber. A Tritium loaded Titanium (“T-Ti”) thick target is located at the other end of the chamber as the cathode. A high voltage (“HV”) power supply is applied between the anode and the cathode. As used herein, “high voltage” means 120-150 kV. The invention only requires a DC power supply of only 12 V or 24 V. A single HV power supply is the only power source for the neutron generator. The Deuterium (“D”) ions are accelerated up to 120-150 kV and bombard the T-target. The nuclear reaction produces fast neutrons (around 14 MeV). A Deuterium-ion beam at the mili-Amp level can produce a neutron yield up to 10 9  n/second. 
         [0015]    The neutron generator of the invention uses field ionization instead of electron ionization in hot cathode or cold cathode ion sources, or Radio-Frequency (“RF”) ionization in RF sources. In one embodiment, CNT or other nanorods are used to generate the high electric field necessary for field ionization of Deuterium. In another embodiment, tungsten multi-tips are utilized to generate the high electric field necessary for gas phase field ionization of Deuterium. At least one of a CNT, NR, or multi-pin tungsten anode is utilized in accordance with the invention. The tungsten tips have a shank diameter of around 80 micrometer with a tip radius of around 100 nanometers (“nm”). This kind of field ionization with tungsten tips is used as ion source at nA level for mass-spectrometry and desktop fusion devices. In the ion source design of this invention, CNT, NR or multi-tip field ionization is used for ion current at the mili-Amp level and then accelerated up to 125-150 kV to get a Deuterium-Tritium (“D-T”) fusion reaction at the T-target. The neutron yield of 10 9  n/s is at the level of conventional commercial neutron tubes. 
         [0016]    A single HV power supply is used for both ion generation and acceleration. In the acceleration process, we do not use any focusing and beam transport systems. The ion beam is allowed, in open geometry, to hit the T-target. This simple accelerator provides two advantages: avoided additional power supply for beam optics and reduced beam power density at the T-target. Consequently, the beam heating is relaxed and the life-time of the neutron generator is increased. The lifetime is much longer than commercial neutron tubes due to the low power density at the T-target. 
         [0017]    In some embodiments of the invention, the generator comprises a remote control. In specific embodiments, the remote control is integrated with the detection system for data collection and analysis. 
         [0018]    The miniature neutron generator is small in size, but can deliver neutron yield comparable with commercial neutron tubes of 10 9  n/second. The generator is small in size, light in weight, economic in power consumption, simple in operation and maintenance and low cost. In one embodiment, the miniature neutron generator is briefcase-sized, weighing less than 10 kilograms (“kg”) and having a battery power supply of 12 or 24 volts. This makes the device easy to carry.