Abstract:
A handheld X-ray fluorescence (XRF) spectrometer is described. The handheld XRF spectrometer comprises a radiation source, a silicon drift detector (SDD), a cooling device configured to regulate the temperature of the SDD, at least one signal processing and power control module coupled to at least one of the radiation source, the SDD, and the cooling device, and a housing substantially encasing the radiation source, the SDD, the cooling device, and the at least one signal processing and power control module. The at least one signal processing and power control module includes at least one input/output connector.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application No. 60/889,890, filed Feb. 14, 2007, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates generally to X-ray fluorescence (XRF) and more specifically to performing elemental analysis using a handheld XRF spectrometer. 
         [0003]    XRF is the emission of characteristic (also referred to as secondary or fluorescent) X-rays from a material that has been excited by, for example, high-energy X-rays, gamma rays, an electron beam, or a radioactive source directed at the material. One specific use of XRF is chemical analysis of a liquid or a solid sample. 
         [0004]    An XRF spectrometer is used to examine the composition of the sample. X-rays are usually irradiated onto a surface of the sample, and the X-ray fluorescence radiation emitted by the sample is detected, the wavelength distribution of the emitted radiation being characteristic of the elements present in the sample, while the intensity distribution gives information about the relative abundance of the sample components. By means of a spectrum obtained in this manner, an expert typically is able to determine the components and quantitative proportions of the examined test sample. 
         [0005]    It is common for known XRF spectrometers to include a sample chamber. During a measurement, the sample is held in a fixed measuring position in the sample chamber. The sample chamber is either evacuated during the measurement or is flooded with an inert gas, such as helium. Performing the measurement under high vacuum prevents air from attenuating the secondary radiation. In order to establish measuring conditions, the sample chamber is connected to a pumping system since, during introduction of a new test sample into the sample chamber, air from the surrounding atmosphere enters the sample chamber and such air is removed from the chamber prior to the actual measurement. Furthermore, known XRF spectrometers also may include a transfer chamber. The transfer chamber is used to facilitate introducing the test sample to the sample chamber. 
         [0006]    With known handheld XRF spectrometers, a sample is placed against the handheld XRF spectrometer that includes a detector. Known handheld XRF spectrometers include traditional detectors such as, for example, Silicon Pin, Cadmium Telluride, Cadmium Zinc Telluride, and Mercuric Iodide detectors. Although portable, handheld XRF spectrometers that include these types of detectors typically are limited by resolution and fluorescence efficiency of the elements being analyzed. Specifically, current handheld XRF spectrometers typically lack the ability to analyze elements with certain Atomic Numbers. 
         [0007]    A tradeoff for portability and ease of use therefore is that such portable spectrometers have a limited range of element analysis as compared to the typical non-portable spectrometer. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    In one embodiment, a handheld X-ray fluorescence (XRF) spectrometer is described. The handheld XRF spectrometer comprises a radiation source, a silicon drift detector (SDD), a cooling device configured to regulate the temperature of the SDD, at least one signal processing and power control module coupled to at least one of the radiation source, the SDD, and the cooling device, and a housing substantially encasing the radiation source, the SDD, the cooling device, and the at least one signal processing and power control module. The at least one signal processing and power control module includes at least one input/output connector. 
         [0009]    In another embodiment, a signal processing and power control module for use with an X-ray fluorescence (XRF) spectrometer that includes a silicon drift detector (SDD) is provided. The module includes at least one system controller configured to provide power and control instructions to at least one of a radiation source and a cooling device. The module also includes at least one signal processor configured to receive operating information from at least one of the radiation source and the cooling device, the at least one signal processor further configured to provide the operating information to a computing device. 
         [0010]    In yet another embodiment, a method of controlling operation of a handheld X-ray fluorescence (XRF) spectrometer that includes a silicon drift detector (SDD) is provided. The method includes configuring a signal processing and power control module to distribute electrical power from a power source to a plurality of components of the XRF spectrometer. The components of the XRF spectrometer are selected to operate within a predetermined voltage range. The method also includes configuring the signal processing and power control module to control operation of at least one of a radiation source and a cooling device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a functional illustration of a detection apparatus. 
           [0012]      FIG. 2  is a perspective view of an exemplary embodiment of a handheld XRF spectrometer. 
           [0013]      FIG. 3  is a schematic diagram of a known handheld XRF spectrometer. 
           [0014]      FIG. 4  is a schematic diagram of a handheld XRF spectrometer including a silicon drift detector. 
           [0015]      FIG. 5  is an enlarged schematic diagram of a nosepiece of a handheld XRF spectrometer including a silicon drift detector. 
           [0016]      FIG. 6  is a block diagram of an XRF spectrometer  80 . 
           [0017]      FIG. 7  is a diagram illustrating power outputs of a signal processing and power control module. 
           [0018]      FIG. 8  is a schematic diagram of a handheld XRF spectrometer including a silicon drift detector, the handheld XRF spectrometer in communication with a processing device. 
           [0019]      FIG. 9  is a cross-sectional perspective view of a nosepiece of a handheld XRF spectrometer including a silicon drift detector. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]      FIG. 1  is a functional illustration of the general components of a detection apparatus  10 . In the illustrated embodiment, detection apparatus  10  is an X-ray fluorescence (XRF) spectrometer  12 . XRF spectrometer  12  includes a primary beam source  14 , and a detector  16 . In the illustrated embodiment, primary beam source  14  is an X-ray tube that projects a primary beam of X-rays  18  towards a sample  20  that is to be tested. In another exemplary embodiment, primary beam source  14  is a radioactive isotope, which projects a primary beam of gamma rays towards the sample  20 . In yet another exemplary embodiment, primary beam source  14  is an electron beam source that projects a primary beam of electrons towards the sample  20 . Any suitable beam source, or plurality of sources, known in the art can be used as primary beam source  14 . 
         [0021]    Sample  20  becomes excited after being exposed to primary beam  18 . This excitation causes sample  20  to emit a secondary (i.e. characteristic or fluorescent) radiation  22 . Secondary radiation  22  is collected by detector  16 . Detector  16  includes electronic circuitry, which is sometimes referred to as a preamplifier, that converts collected secondary radiation to a detector signal  24  (i.e., a voltage signal or an electronic signal) and provides the detector signal  24  to an analyzer  26 . In one embodiment, analyzer  26  includes a digital pulse processor. While illustrated as a non-handheld unit, detection apparatus  10  illustrates the major components that are also utilized in a handheld spectrometer. 
         [0022]      FIG. 2  is perspective view of an exemplary embodiment of a handheld XRF spectrometer  40 . Handheld XRF spectrometer  40  includes a housing  42 . Housing  42  encloses and protects the internal assemblies of handheld XRF spectrometer  40 . 
         [0023]    Housing  42  of handheld XRF spectrometer  40  includes a nosepiece  44  and a body  46 . In an exemplary embodiment, housing  42  may have a “handgun-shaped” profile, with a handle  48 , extending from body  46 . Handle  48  may be positioned such that the user may comfortably hold handle  48  and direct nosepiece  44  to a desired position. Handheld XRF spectrometer  40  includes components similar to those described with respect to  FIG. 1 , including a detector, a beam source, and an analyzer. 
         [0024]    In an exemplary embodiment, housing  42  may be composed of one, or a combination of the following: ABS plastics, and alloy materials such as Magnesium, Titanium, and Aluminum. Housing  42  may be composed of any material with the strength to encase and protect the internal components of handheld XRF spectrometer  40 . This protection may include, but is not limited to, protection from elements such as wind and rain, protection from dust and other impurities, and protection from damage caused by dropping spectrometer  40  onto a surface or from rough handling of spectrometer  40 . This protection may also be bolstered through the use of over molding, rubber bumpers, shock absorbing mounts internal to the instrument assembly, and/or the use of crushable impact guards. 
         [0025]    In one embodiment, housing  42  is composed of lightweight materials, as when in use, handheld XRF spectrometer  40  is held by one of a user&#39;s hands. A light weight handheld XRF spectrometer  40  increases maneuverability and increases the ease-of-use of handheld XRF spectrometer  40  over a heaver handheld spectrometer. 
         [0026]      FIG. 3  is a schematic diagram of a known handheld XRF spectrometer  50 . An X-ray tube  58  is positioned within a nosepiece  54 . X-ray tube  58  directs primary X-rays through a collimator  60 . Collimator  60  is configured to allow X-rays traveling parallel to a specified direction to pass through. A detector  62  is also positioned within nosepiece  54 . In known handheld XRF spectrometers, detector  62  includes one of a silicon pin detector, a cadmium telluride detector, and a mercuric iodide detector. Nosepiece  54  also includes a preamplifier  66 . Preamplifier  66  amplifies voltage signals produced by detector  62  that correspond to the secondary radiation received by detector  62 . Preamplifier  66  also provides the voltage signals to a digital pulse processor  68  for final processing. 
         [0027]    Detector  62  typically includes a cylindrical wafer of semiconductor material with rectifying p or n contacts on a top and a bottom of the detector forming a diode. The diode is cooled on its bottom side by, for example, a single or double stage Peltier cooler. Detector  62  has a bias voltage across it to move the electrons generated by the colliding photons from the sample to a collection point. The typically negative bias voltage on the front of the detector attracts the holes generated in the semiconductor and repels the electrons. A negative charge cloud is generated that drifts to the rear contact and is converted by, for example, a Field Effect Transistor (FET) to a voltage signal with a shape corresponding to the detected secondary radiation. 
         [0028]    The number of electrons produced in the negative charge cloud is directly proportional to the energy of the secondary radiation collected by the detector. The amount of charge collected creates a voltage pulse of a magnitude that is directly proportional to the energy of the detected secondary radiation. The diode, Peltier cooler, and FET are located in a high vacuum metal enclosure, for example a Nickel enclosure, which includes a window that enables the secondary radiation to reach the front of the diode. The diode leads to electrical connectors that pass through the bottom of the detector enclosure and attach bias voltage, supply Peltier cooler power, and lead to a preamplifier. 
         [0029]    The level of capacitance between the detector anode to ground demands signal noise filtering with high time constants (i.e., 10-20 uSec). The high time constants unfavorably limit the detector throughput to counts per second in the range of tens of thousands counts per second. However, the high time constants allow for the use of low bandwidth electronics (i.e., 1 MHz), which is beneficial because typically low bandwidth electronics consume less power and more easily handle noise than higher bandwidth electronics. In addition, in typical XRF spectrometers  50 , individual components utilize different operating voltage levels. Multiple power sources may provide these various voltage levels and/or conditioning circuits may change the power levels within the spectrometer  50 . 
         [0030]      FIGS. 4-8  are various illustrations of a handheld XRF spectrometer  80  that includes a silicon drift detector (SDD)  82 . More specifically,  FIG. 4  is a schematic diagram of handheld XRF spectrometer  80  that includes SDD  82 . Handheld XRF spectrometer  80  is encased in a housing, similar to housing  42  described above, and includes a nosepiece  88  and a body (not shown in  FIG. 4 ). In an exemplary embodiment, the housing has the same profile as housing  42  (shown in  FIG. 2 ). In an exemplary embodiment, housing  42  has overall dimensions of less than thirty cubic centimeters and a weight of less than or equal to two kilograms. 
         [0031]    SDD  82  is contained in a protective enclosure, for example, an enclosure composed of nickel or stainless steel. The protective enclosure also includes a thin window  112 . In an exemplary embodiment, thin window  112  is composed of Beryllium. Thin window  112  allows for electronic shielding and ambient light shielding while allowing secondary radiation to pass through. The protective enclosure also includes at least one sealed electrical contact  120  that extends through the walls of the enclosure. The at least one electrical contact  120  provides a connection between a plurality of preamplifiers including, in one embodiment, a preamplifier  122  and a preamplifier  124 . The at least one electrical contact  120  also provide at least one biasing voltage to SDD  82 . As described above, a secondary radiation may be attenuated by air, therefore a vacuum or an area flooded with inert gas is maintained by the protective enclosure to prevent this attenuation. 
         [0032]    Handheld XRF spectrometer  80  includes a signal processing controller  126  that receives and processes an electrical signal from SDD  82  that corresponds to detected secondary radiation. In an exemplary embodiment, controller  126  includes preamplifier  124 , at least a third pre-amplification stage  130 , and a digital pulse processor  132 . Preamplifiers  124  and  130  provide an interface for signals propagating between SDD  82  and digital pulse processor  132 . In XRF spectrometer  80 , signal processing controller  126  also provides functions relating to system control, cooler control, and power distribution and is further described as a signal processing and power control module below. To provide a handheld XRF spectrometer that incorporates a silicon drift detector, one or more circuits that support and provide an interface to SDD  82  are incorporated into handheld spectrometer  80 . It should be recognized that handheld XRF spectrometer  80  includes additional preamplifier circuits  124  and  130 , which are provided to support operation of SDD  82  and the interface between SDD  82  and digital pulse processor  132 . 
         [0033]      FIG. 5  is an enlarged schematic diagram of nosepiece  88  of handheld XRF spectrometer  80  of  FIG. 4 . Handheld XRF spectrometer  80  includes a radiation source  138 . Radiation source  138  may include, but is not limited to, an electron beam source, a radioisotope source, a pyroelectric source, and an X-ray tube. In the illustrated embodiment of  FIG. 5 , radiation source  138  is an X-ray tube. X-ray tube  138  directs a primary X-ray beam  140  toward a primary beam collimator  142 . A primary beam collimator  142  allows X-rays oriented in a particular manner to pass through and irradiate a sample  144 , which is in a position to be tested. 
         [0034]    After sample  144  is exposed to primary X-ray beam  140 , the material of sample  144  is excited and secondary X-rays  146  are emitted by sample  144 . Secondary X-rays  146  are detected by SDD  82 . A suitable SDD  82  is commercially available from KETEK GmbH, of Munich, Germany. SDD  82  may be purchased, for example, in a standard TO8 transistor housing. 
         [0035]    SDD  82  is typically fabricated using high-purity n-type silicon by providing at the entering photon side a large area pn-junction and the opposite side a central spot n-doped anode that is surrounded by a number of concentric p-type drift rings. During operation of SDD  82 , the pn-junctions on both sides of the silicon are biased in reverse, generating a minimum of free electrons in the bulk. 
         [0036]    By generating a voltage gradient across the drift rings, a traversal electric field is generated which bends the potential across each ring and forces the electrons to drift to the anode. The small capacitance of the anode together with the low leakage current of the silicon enable low noise and fast readings of the electron signal generated from the photon interaction with the detector surface. Each ring has a separate bias voltage and dedicated electronics for handling those voltages. 
         [0037]    The low anode capacitance demands a time constant for optimal signal filtering to be of an order of magnitude less than those usual for Silicon PIN type detectors. The low time constant allows for a high throughput (e.g. hundreds of thousands and approaching millions of counts per second). Utilization of SDD  82  and signal processing techniques as further described below, allow for analysis times of ten seconds or less, and in certain analysis scenarios, analysis times less than one second. The low time constant also allows for a high signal to noise ratio, which results in an SDD having a high resolution. The high signal to noise ratio also allows the SDD to work at high temperatures. However, in an exemplary embodiment, the bandwidth of the signal processing electronics is increased in order to process the high throughput from the SDD. Compensation for noise in a higher bandwidth electronic circuit typically requires electronics that consume a greater amount of power than in a lower bandwidth electronic circuit. 
         [0038]      FIG. 6  is a functional block diagram of XRF spectrometer  80 , described above. Power is supplied to XRF spectrometer  80  by a power supply  150 . In an exemplary embodiment, power supply  150  is a battery or multiple batteries combined to produce a voltage and current. The battery provides appropriate voltages and currents to a power distribution network, while adding to the maneuverability of XRF spectrometer  80  by eliminating electrical power cords. Spectrometer  80  includes functions relating to system control  152 , cooler control  154 , and signal processing  156 . A computing device  160  is also included in a specific embodiment. In one embodiment of XRF spectrometer  80 , these functions are combined on a single signal processing and power control module (shown in  FIG. 7 ). 
         [0039]    Radiation source  138 , in one example an X-ray source, receives power and control instructions from system controller  152 . X-ray source  138  reports information on the operation of X-ray source  138  to signal processor  156 . Signal processor  156  receives operating information from a cooler controller  154  and provides operating information from X-ray source  138  and cooler controller  154  to a computing device  160 . Cooler controller  154  provides regulated temperature control to SDD  82 . In one embodiment, cooler controller  154  controls a Peltier cooler that is positioned to lower the temperature at SDD  82 . 
         [0040]    In operation, SDD  82  receives secondary radiation emanated from a sample, converts the received radiation into an electrical signal, and provides the electrical signal to signal processor  156 . Signal processor  156  routes the electrical signal to computing device  160  for processing and display. 
         [0041]    In an exemplary embodiment, system controller  152  supplies SDD  82  with a plurality of separate bias voltages, as described above. Also, signal processor  156  is configured to analyze a plurality of electrical signals output by SDD  82 . 
         [0042]    In an embodiment described above, power supply  150  is a battery. In this embodiment, low power consumption by XRF spectrometer  80  increases the time XRF spectrometer  80  can operate before the battery looses its charge. The battery must either be replaced or recharged when the battery can no longer supply the voltages and currents necessary for operation of XRF spectrometer  80 . 
         [0043]    In an exemplary embodiment, illustrated in  FIG. 7 , XRF spectrometer  80  includes a signal processing and power control module  180  which, in part, provides power to the internal components of XRF spectrometer  80 . In an exemplary embodiment, signal processing and power control module  180  includes at least one rigid circuit board that interconnects components of the module  180 . However, in alternative embodiments, module  180  may include at least one flexible circuit board or any other component interconnections that facilitate operation of module  180  as described herein. Outputs of the power control portion of module  180  are sometimes referred to as a supply rail. Examples of power outputs from module  180  are shown in  FIG. 7  and include one or more of bias voltages, a cooler power supply voltage, various field programmable gate array (FPGA) power voltages, ramp power, charge pump power, and analog-to-digital converter power. Internal components utilized on module  180  are selected to operate within a common voltage range, which reduces the number of buffers and signal conditioning components included in XRF spectrometer  80 . By eliminating or reducing the number of power conversions necessary to in providing the functions of signal processing and power control module  180 , a source of power loss is reduced, and the physical size of the power supply circuits are thus reduced. 
         [0044]    In an embodiment, suspended operation, standby, and power-down modes are incorporated into module  180  to reduce the amount of power that is drawn from the battery. Suspended operation, standby, and power-down modes either reduce the amount of power provided to a particular component of XRF spectrometer  80  or discontinue providing power to a particular component of XRF spectrometer  80  for a period of time. For example, power may be suspended to X-ray source  138  between sample assessments. After power is re-applied to X-ray source  138 , stability is not reached until a time period has passed. However, that time period may be used to lower the temperature of SDD  82  after the temperature of SDD  82  was allowed to rise to a power saving standby temperature by discontinuing or reducing power to cooler controller  154  when SDD  82  was not in use. 
         [0045]    In another exemplary embodiment, suspended operation may include providing components of XRF spectrometer  80 , including in one example, components of module  180 , with a reduced amount of power with which to operate. The reduced amount of power may reduce the performance of these components by reducing clock frequency and/or disabling performance enhancing parts. However, even in this low-power mode, power is kept at a level where XRF spectrometer  80  is functional. By operating XRF spectrometer  80  in a low-power mode when maximum clock speeds are not necessary, battery power is conserved. 
         [0046]    Due to the limited amount of power supplied by a battery sized with portability in mind, the output of X-ray source  138  does not reach the maximum pulse processing capacity of SDD  82 . This mismatch between the pulse processing power of SDD  82  and the available X-ray power may be used to reduce power consumption. In another exemplary embodiment, XRF spectrometer  80  is operated in a pulsed mode. In the pulsed mode, XRF spectrometer  80 , and in particular signal processing and power control module  180 , includes at least one power storage capacitor. While the power storage capacitor is being charged, analysis of a sample does not occur. Instead, analysis of a sample occurs while X-ray source  138 , SDD  82 , and controller  126  are provided with short pulses of power from the power storage capacitor. The short pulses of X-rays are processed at the full native speed of SDD  82 . 
         [0047]    In yet another exemplary embodiment, power consumption of XRF spectrometer  80  may be reduced by operating in an intermediate mode. In the intermediate mode, as in the pulsed mode, analysis of a sample does not occur while the power storage capacitor is being charged. However, in the intermediate mode, secondary radiation is collected by SDD  82 , which is powered by the battery, while X-ray source  138  is powered by the power storage capacitor. 
         [0048]    In yet another exemplary embodiment, power consumption of XRF spectrometer  80  may be reduced by limiting the power consumed by module  180 . In this embodiment, module  180  is intermittently provided with power, from a time period before an X-ray is emitted from X-ray source  138 , to a time period after the signal from SDD  82  is processed by module  180 . Providing module  180  with power at the desired times may be achieved in a variety of ways. In one embodiment, statistics based on mean count rates and signal history can provide a prediction of when power should be provided to module  180 . In another embodiment, a delay line, such as a low-power analog delay line (e.g., CCD, acoustic surface waves, ultrasonic delay line, delay cable, LC delay line), is included in XRF spectrometer  80 . A signal inspector is connected to the input, or near the input, of the delay line. The signal inspector, along with the output of the delay line, is also connected to module  180 . Upon detecting a signal at the input of the delay line, the signal inspector switches on power to module  180 . When the signal reaches the output of the delay line, controller  126  is prepared to receive it. 
         [0049]    Combining of power control functions and signal control functions in a single module may not allow for complete separation between the frequency ranges of the supply circuits and the frequency ranges of the signal processing circuits. Shifting the switching frequency of the power circuits above the passband of the signal processing circuits, in situations where that shift is possible, may reduce efficiency due to inherently lossy components (e.g., switching loss). Additionally, because the power spectrum of switched mode power supplies spreads over all harmonics of the fundamental frequency, simply shifting power supply switching frequency below the passband of the signal processing circuits is also not efficient. 
         [0050]    In certain signal processing schemes, zeroes of the transfer functions exist even near the passband. For example, the transfer function of a gated integrator with respect to noise suppressing is more or less described by the term sin(x)/x which exhibits unlimited number of zeros at x=n* Pi (n=1 . . . ). Signal processing and power control module  180  is configured such that the operating frequencies of possible noise sources are adjusted in a way that potentially interfering signal frequencies match the zeros in the transfer function. Such a configuration results in noise reduction. 
         [0051]    In another embodiment of module  180 , potential noise sources are operated synchronously, preferably at the same clock or at multiples of a common master clock. Synchronous operation of potential noise sources may occur with, or instead of, matching of signal frequencies, as is described above. In a further embodiment, adaptive phase shifting is utilized in module  180  which results in different noise sources canceling one another out. 
         [0052]    As stated above, noise reduction circuitry typically requires power, and is therefore a drain on a system powered by a battery. A variety of approaches may be utilized to improve noise immunity of the electronic circuitry of XRF spectrometer  80 . In an exemplary embodiment, to improve noise immunity, which in turn may reduce the power consumption of noise reduction circuitry,  3 D simulation may be used to design routing traces along equi-potentials and/or position compensating lines. In another exemplary embodiment, noise susceptive components are replaced by more immune components. In yet another exemplary embodiment, active noise cancelling is implemented by positioning noise sensing loops near critical signal traces. Any other known methods of improving noise immunity may be used to reduce the noise within the electrical circuits of XRF spectrometer  80 . 
         [0053]      FIG. 8  is a schematic diagram of handheld XRF spectrometer  80  in communication with a computing device  160 . In example embodiments, computing device  160  may include one or more of a microprocessor, processor, microcontroller, microcomputer, programmable logic controller, application specific integrated circuit, and other programmable circuits. In another alternative embodiment, computing device  160  may include one or more of a personal computer, a server, a personal digital assistant, and any other device capable of receiving and processing data from handheld XRF spectrometer  80 . In the illustrated embodiment, computing device  160  includes an output display  162 . Output display  162  may be a printer, a screen, or any other device that allows a user to view an output from computing device  160 . Computing device  160  may also include an input device (not shown in  FIG. 8 ). The input device may include one or more of a keypad, touch screen, jog dial, microphone, and any other input device capable of providing instructions from a user to at least one of computing device  160  and handheld XRF spectrometer  80 . 
         [0054]    In the illustrated embodiment, cables  166  and  168  provide a path for at least one of data communications between handheld XRF spectrometer  80  and computing device  160  and electrical power between handheld XRF spectrometer  80  and computing device  160 . However, this link is not limited to only a cable or a wire. In another exemplary embodiment, handheld XRF spectrometer  80  and computing device  160  include wireless capabilities, for example, Bluetooth® wireless capabilities. Bluetooth® is a registered trademark of Bluetooth SIG of Bellevue, Wash. 
         [0055]      FIG. 8  also illustrates a power input  170  positioned on handheld XRF spectrometer  80 . In one exemplary embodiment, power input  170  is a port configured to receive a plug that connects power input  170  to a power source, for example, a standard electrical outlet or other power supply. In another exemplary embodiment, power input  170  is a pair of battery terminals. In yet another exemplary embodiment, power input  170  provides a connection between a battery within handheld XRF spectrometer  80  and a battery charger. In this embodiment, the battery charger is connected to an external power supply and configured to charge the battery of XRF spectrometer  80  when connected. The handheld XRF spectrometer  80  is encased within a housing, as described above. In this exemplary embodiment, the housing includes a battery holder (not shown in  FIG. 5 ) configured to secure at least one battery within the housing. The battery holder is also configured to align the terminals of the batteries with the corresponding power input  170  of handheld XRF spectrometer  80 . In exemplary embodiments, it is desirable for the at least one battery to have a high energy storage capacity such as a for example, Lithium ion battery, a Lithium polymer battery, or a fuel cell. 
         [0056]      FIG. 9  is a cross-sectional perspective view of nosepiece  88  of handheld XRF spectrometer  80  incorporating SDD  82  of  FIGS. 4-7 . Components that are common to  FIGS. 4-7  are illustrated with the same reference numerals. In an exemplary embodiment, radiation source  138  (shown in  FIG. 4 ) is positioned at a location  182 , and thin window  112  (shown in  FIG. 4 ) is positioned at an opening  184  within nosepiece  88 . 
         [0057]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.