Scott Pellegrin

A Multichannel Nanoparticle Scintillation Microdevice with Integrated Waveguides for Alpha, Beta, Gamma, X-Ray, and Neutron Detection

This paper reports on a glass microdevice with a new patterned nanoparticle composite resin that detects and discriminates all species of radiation emitted from fissionable bomb making materials. Tailored charge conversion nanoparticles doped into a fast electron scintillating resin produce different optical pulses specific to the radiation species. The resins are integrated into a glass substrate where deep cavities are made using microsandblasting, forming independent optical paths leading to fiber-optic attachments. A separate, off the shelf Photo-Multiplier (PM) tube measures the light pulse.

Integrated System for Wireless Radiation Detection and Tracking

This paper reports on an integrated system of wirelessly linked radiation detectors. A small radiation detector is combined with a pulse counting circuit to record radiation pulses in the area of the detector. Multiple sensors are mesh networked together using wireless radios. Mesh networking allows for a large network of battery powered nodes with only one receiving hub. Radiation data is communicated to a central location where it is compared to the location of the node and its relative position to the other nodes. This information is used to locate and track a radiation source.

A Multichannel Nanoparticle Scintillation Microdevice With Integrated Waveguides for Alpha, Beta, Gamma, X-Ray, and Neutron Detection

This paper reports on a glass microdevice with a new patterned nanoparticle composite resin that detects and discriminates all species of radiation emitted from fissionable bombmaking materials. Tailored charge conversion nanoparticles doped into a fast-electron scintillating resin produce different optical pulses specific to the radiation species. These pulses exit since the nanoparticles are appreciably smaller than the wavelength of light. The resins are integrated into a glass substrate where deep cavities are made using microsandblasting, forming independent optical paths leading to fiber-optic attachments. Separate off-the-shelf photomultiplier tubes measure the light pulses. The beta detector was tested with a 90Sr source which produced 1470 cpm with the doped scintillator, while the same source produced 1500 cpm with an off-the-shelf Geiger counter. An Am/Be neutron source was used to test Gd-loaded detectors which exhibited an increase in count rates with an increase in Gd loading. The different nanoparticles used convert differing radiation species into electrons through independent physical mechanisms, including charge conversion (alpha), secondary electron (beta), photoelectron (gamma/X-rays), and an on-chip thermonuclear fusion reaction (neutron) to evaluate the specific isotope radiation signature. The four different detectors use four different methods to convert four different types of radiation into electrons; as a consequence, the measured pulses are characteristic to the radiation, allowing pulse height spectroscopy to be used.

Glass and Quartz Microscintillators for CMOS Compatible Multi-Species Radiation Detection

This paper reports small scale radiation detectors sensitive to alpha, beta, gamma, and neutron radiation using glass and quartz doped with 10B nanoparticles utilizing CMOS fabrication techniques. Two microscintillators have been fabricated and tested; one relies on sintered glass frit doped with boron nanoparticles; the other relies on diffused boron. Radiation impinging the scintillation matrix produces varying optical pulses which are differentiated by on-chip pulse height spectroscopy. The quartz substrates are more transparent to the wavelength of the created optical pulses, resulting in higher count rates when compared to glass.

Radiation scintillator embedded with a converting medium to detect and discriminate the four species of ionizing radiation

A new nanoparticle loaded plastic scintillator embedded in a glass substrate detects and discriminates all species of radiation emitted from fissionable bomb making materials. The fast electron scintillating resin is doped with tailored charge conversion nanoparticles to produce characteristic optical pulses. The created optical pulses exit the detector, since the nanoparticles are appreciably smaller than the wavelength of light. Microsandblasting is used to etch deep cavities in the glass substrate forming independent optical paths. The doped resin is injected into the cavities and cured. A separate off-the-shelf PM tube linearly amplifies the created light pulse into a usable electrical signal. By using tailored nanoparticles, the physical mechanisms for converting different species of radiation into lower energy electrons allows for pulse height spectroscopy to discriminate between alpha, beta, gamma, and neutron radiation. A 90Sr source was used to test the beta detector, which is loaded with W. The drop in count rates versus distance was found to be similar to traditional detectors. The gamma detector loaded with Pb nanoparticles was tested with a 60Co source. The addition of Pb provided greater sensitivity to the gamma radiation. A 210Pl source was used to test the glass doped scintillator. The count rates remained fairly constant for varying distances since alpha particles tend to travel in straight paths until losing most of their initial energy. The 157Gd loaded scintillator was tested with an Am/Be source. 157Gd has the largest thermal neutron absorption cross section at 255,000 barns and releases a usable characteristic 72keV electron in 39% of the capture reactions.

A Nanoparticle Doped Micro-Geiger Counter for Multispecies Radiation Detection

This paper reports on a multichannel radiation detection platform enabled with nanoparticles that is capable of detecting and discriminating all types of radiation emitted from fissionable bomb making materials. Typical Geiger counters are limited to detecting only beta and gamma radiation. The micro-Geiger counter reported here detects all species of radiation including beta particles, gamma/X rays, alpha particles, and neutrons. The multispecies detecting micro-Geiger counter contains a hermetically sealed and electrically biased fill gas. Impinging radiation interacts with tailored nanoparticles to release secondary charged particles that ionize the fill gas. The ionized particles collect on respectively biased electrodes resulting in a characteristic electrical pulse. Pulse height spectroscopy and radiation energy binning techniques can then be used to analyze the pulses to determine the specific radiation isotope. The ideal voltage range of operation for energy discrimination was found to be in the proportional region at 1000 Vdc. In this region, specific pulse heights for different radiation species resulted. The amplification region strength which determines the device sensitivity to radiation energy can be tuned with the electrode separation distance. An electrode separation of 0.8 mm produced a count rate of 530 cpm for a 90Sr beta source when compared to an off-the-shelf Geiger counter which produced 1500 cpm. Count rates as high as 15 300 were observed for the same radiation source with electrodes spaced closer than 0.5 mm. By using a novel microinjection ceramic molding and silver paste metallizing process, the batch fabrication of essentially disposable devices can be achieved.

A charge conversion nanoparticle enhanced microGeiger for alpha, beta, gamma, and neutron detection

This paper reports on a radiation detection platform that uses charge conversion nanoparticles to detect and discriminate all types of radiation. Previous microGeigers only detect beta particles. The microGeiger reported here detects beta particles, along with gammas, alphas and neutrons. The multi-species detecting microGeiger counter contains a biased fill gas that becomes ionized when impinging radiation interacts with tailored nanoparticles to release secondary charged particles. The ionized particles then collect on respectively biased electrodes to register characteristic pulse heights which are analyzed with pulse height spectroscopy techniques. The microGeiger counter uses ceramic injection molding processes to batch fabricate inexpensive devices that are essentially disposable.

Glass and Quartz Microscintillators for CMOS-Compatible Multispecies Radiation Detection

This paper reports on a small-scale radiation detector that is sensitive to alpha, beta, gamma, and neutron radiation using scintillators doped with boron nanoparticles utilizing CMOS fabrication techniques. Two types of microscintillators have been fabricated and tested: One relies on sintered glass frit doped with boron nanoparticles, and the other uses quartz with boron diffused into the substrate. Radiation impinging on the scintillation matrix produces varying optical pulses of varying intensities depending on the type of radiation particle. The optical pulses are differentiated by on-chip pulse height spectroscopy and recorded on a microcontroller. The pulse height circuitry has been fabricated with both discrete circuits and designed into a single integrated circuit package. The quartz substrates have shown to be more transparent to the wavelength of the created optical pulses, which results in a higher count rate when compared to the tested glass scintillator. The quartz scintillator also shows better absorption of radiation particles, resulting in better detection efficiencies than the glass. The quartz also has been tested with varying doping levels and has the ability to detect neutrons. Source differentiation between 137Cs and 60Co has also been demonstrated.

Nanostructured neutron detectors with on chip integrated circuits for space flight monitoring

This paper reports on a complete integrated system for radiation detection in harsh field environments, for example monitoring radiation exposure for astronauts or detecting nuclear fissionable materials. Charge conversion nanoparticles doped into a fast electron scintillating resin produce optical pulses specific to neutron radiation. These pulses exit the material since the nanoparticles are smaller than the wavelength of light. An off the shelf Photo-Multiplier (PM) tube converts the created light pulses into a usable electrical signal. The signal is amplified by a charge sensitive preamplifier which integrates the current to produce a signal that represents the total charge deposited inside the scintillator. The signal is further shaped by circuitry and converted to a digital signal and stored by a microprocessor. Constructing integrated circuits for pulse shaping and power conversion allows for a fully functioning detector able to operate as a standalone unit.

A Dual Layer Scintillation Microdevice for Gamma and Beta Particle Energy Spectroscopy

This paper reports on a multichannel radiation detector capable of energy spectroscopy of beta and gamma radiation. The scintillation microdevice consists of a double layer array of two patternable scintillating polymer films stacked with different optical decay constants. The top patterned layer of the detector has a small decay constant and is doped with tailored charge conversion nanoparticles to produce different optical pulses specific to the radiation species. The decay constant of the bottom patterned layer is orders of magnitude larger which produces different optical pulses that are measured by an off the shelf photo-multiplier (PM) tube.