Patent Application: US-64990709-A

Abstract:
the present invention is an electrically controlled gettered pump assembly to entrain and fully release hydrogen gas to regulate the pressure and buffer the ions in an ion trap mass spectrometer and other portable analytical instruments . in addition to the gettered pump assembly , the present invention also incorporates a microvalve between the different chambers to release and control the hydrogen content . hydrogen gas regulates the pressure in mass spectrometers and also acts as a buffering gas to prevent the ions from escaping the trap .

Description:
while the making and using of various embodiments of the present invention are discussed in detail below , it should be appreciated that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts . the specific embodiments discussed herein are merely illustrative of specific ways to make and use the invention and do not delimit the scope of the invention . to facilitate the understanding of this invention , a number of terms are defined below . terms defined herein have meanings as commonly understood by a person of ordinary skill in the areas relevant to the present invention . terms such as “ a ”, “ an ” and “ the ” are not intended to refer to only a singular entity , but include the general class of which a specific example may be used for illustration . the terminology herein is used to describe specific embodiments of the invention , but their usage does not delimit the invention , except as outlined in the claims . it is contemplated that any embodiment discussed in this specification can be implemented with respect to any method , kit , reagent , or composition of the invention , and vice versa . furthermore , compositions of the invention can be used to achieve methods of the invention . research in the field of microsensors has provided a great impetus to the development of smaller instrument components . among these developments , are included small , low power ion sources , such as field emitters , which produce a high electron current with minimal power requirement . miniaturization of mass spectrometry applications has resulted from the development portable vacuum and turbo pumps . research groups are active in the development of submillimeter ion trap , rectilinear ion trap , micron sized ion trap arrays , and mini time - of - flight ( tof ) detectors . ion detection has also been made microscale with small channeltron and microchannel plate ( mcp ) detectors from detech and burle . researchers have been successful in developing sub - mm cylindrical ion - traps ( moxom , et al ., and moxom et al . ), small rectilinear traps ( sokol , et al . ), toroidal ion trap ( lammert et al . ), miniature tof mass spectrometer ( brinckerhoff , et al .). research efforts are also underway in trying to miniaturize the rotating - field mass spectrometers and small sectors , however these efforts have met with only limited success to date . resolution and ion attenuation are the two major challenges facing current miniature devices . decreased ion attenuation is directly related to the small device size . with smaller devices space - charge and surface - charge effects increase , decreasing the number of ions trapped or guided . for ion - traps the maximum number of ions ( n max ) stored is directly proportional to the depth of the pseudo - potential well ( d z ) ( dawson ), as shown in equation 1 below : a typical z = 1 cm trap will hold 10 6 - 10 7 ions . as the trap gets smaller by an order of magnitude , so does the ion count . a z = 1 mm trap will hold approximately 10 5 ions . one way to overcome this deficit is to array the ion traps to regain ion count . if this is done , alignment becomes critical due to ion ejection from multiple traps . resolution ( m / δm ), increases with increasing time . resolution and time are related by equations 2 , 3 , and 4 for tof , linear quad ( lq ) and qit mass spectrometers , respectively : tof and lq mass spectrometers are the most difficult to miniaturize without compromising the resolution , as the resolution is length dependent . use of a reflectron or passing the ion back and forth are approaches that can be used to increase the time of flight within a more confined space . qit and cylindrical ion traps can have increased resolution within a miniature device . trapping time can be increased to increase resolution at the expense of signal attenuation . with the increasing use of miniature mass spectrometers , small sems , chemical sensors and vacuum devices , in analytical research , among first responders , military , environmentalists , tsa , and field researchers there is a growing need to run these devices without carrying high pressure gas cylinders to pressurize and maintain vacuum conditions required to run these devices . hydrogen gas is typically used regulate pressures and act as a buffer to thermalize the trapped ions in these devices . in addition to maintaining the vacuum , the buffer gas at pressures of approximately 1 × 10 − 4 torr is needed to keep the ions from escaping the trap . lq &# 39 ; s and ion mobility spectrometers also require pressure regulation at vacuum . the present invention obviates the use of cumbersome high - pressure gas cylinders to operate miniature mass spectrometers and other portable vacuum devices . the present invention makes use of getters saturated with hydrogen to regulate the pressure in mass spectrometers and also utilizes the gas for buffering the ions . these getters ( i . e . titanium and zirconium ) have been used as pumps and hydrogen sources previously but never to regulate pressures in portable vacuum devices requiring regulated hydrogen supply . the getters are current controlled to produce the necessary hydrogen number density , with a microvalve implemented between the chambers to release and control hydrogen content . the following diagrams illustrate the technology invented and subsequent explanation of each component of the invention . fig1 a is a schematic illustration of a single cit 101 . the ion trap 101 comprises a cylindrical ring electrode 107 , and two endcap electrodes at the top and the bottom 103 and 105 , respectively . 113 and 115 represents the dielectric spaces between the ring electrode 107 and the endcap electrodes 103 and 105 , respectively . the ions are trapped in the space 117 between the end cap electrodes 103 and 105 and the ring electrode 107 . openings 109 and 111 are made in the top and bottom electrodes 103 and 105 , for injection of the ionized sample and for the ejection of the ions from the space 117 . the cit 101 is rotationally symmetric about the z - axis . r is the inner radius of the ring electrode 107 . a power source ( not shown in the figure ) can be used to provide dc and rf voltage to the cit 101 . v t represents the voltage between the top and the bottom electrodes 103 and 105 , and v o represents the voltage applied to the ring electrode 107 . fig1 b shows the voltage profile across a section of a cit 101 . voltages across the endcap electrodes 103 and 105 decrease axially towards the center of the cit . voltages across the ring electrode 107 increase radially towards the center of the cit 101 . fig2 a shows a template 119 on which is present an array of cylindrical ion traps . fig2 b is an expanded view of a microfabricated array of cylindrical ion traps . the supporting template or metallic plate 121 , comprises of cylindrical holes 123 a , 123 c , 123 e , 123 g , 123 i , 123 k , 123 m , 123 o , 123 q , 123 s , 123 u , 123 w , 123 y , 123 aa , and 123 ac . extraction holes 123 b , 123 d , 123 f , 123 h , 123 j , 123 l , 123 n , 123 p , 123 r , 123 t , 123 v , 123 x , 123 z , 123 ab , and 123 ad , are present on the cylindrical axis of each of the cylindrical holes listed above . fig3 is a schematic of a cit mass spectrometer 125 . the cit mass spectrometer 125 , comprises of a macor ® sleeve 127 , and ionizer 129 to ionize the sample . a voltage can be applied to the tuning lens 131 , to regulate and direct the passage of the generated ions to the ion trap 133 . the ion trap 133 , comprises of a ring electrode 133 b and two end cap electrodes 133 a and 133 c . a channeltron ® device 135 is used to detect the ions ejected from the ion trap and measures the total ion current . fig4 is a computer aided design of the interior of an ion trap 139 of a cit mass spectrometer 137 . ion trap 137 comprises three gettered pumps 139 , 141 , and 143 for sorbing and releasing hydrogen gas to maintain the pressure and as a buffer to thermalize the ions . ion trap 137 also has a microvalve 145 to release and control hydrogen content inside the ion trap 139 . fig5 is a computer aided cross - sectional design of a cit mass spectrometer 149 , comprising a macor ® sleeve 151 , an ionizer 153 , and a tuning lens 155 . the ion trap chamber 157 comprises a microfabricated cylindrical ion trap array 157 a , and three gettered pumps 159 , 161 , and 163 for sorbing and releasing hydrogen gas to maintain the pressure and as a buffer to thermalize the ions . fig6 shows the relationship between the gettering rate ( ml / sec ) versus the quantity sorbed ( ml / torr ) at 900 ° c . for 10 minutes studied for hydrogen , nitrogen , oxygen and carbon monoxide . the logarithmic plot indicates a decrease in the gettering rate with the increase in the amount of the sorbed gas . the decrease in rate is greater for n 2 , o 2 , and co when compared to h 2 , thus indicating the effectiveness of the gettering system of the present invention for sorbing h 2 . fig7 and 8 show mass spectra obtained using the present invention it will be understood that particular embodiments described herein are shown by way of illustration and not as limitations of the invention . the principal features of this invention can be employed in various embodiments without departing from the scope of the invention . those skilled in the art will recognize , or be able to ascertain using no more than routine experimentation , numerous equivalents to the specific procedures described herein . such equivalents are considered to be within the scope of this invention and are covered by the claims . all publications and patent applications mentioned in the specification are indicative of the level of skill of those skilled in the art to which this invention pertains . all publications and patent applications are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference . the use of the word “ a ” or “ an ” when used in conjunction with the term “ comprising ” in the claims and / or the specification may mean “ one ,” but it is also consistent with the meaning of “ one or more ,” “ at least one ,” and “ one or more than one .” the use of the term “ or ” in the claims is used to mean “ and / or ” unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive , although the disclosure supports a definition that refers to only alternatives and “ and / or .” throughout this application , the term “ about ” is used to indicate that a value includes the inherent variation of error for the device , the method being employed to determine the value , or the variation that exists among the study subjects . as used in this specification and claim ( s ), the words “ comprising ” ( and any form of comprising , such as “ comprise ” and “ comprises ”), “ having ” ( and any form of having , such as “ have ” and “ has ”), “ including ” ( and any form of including , such as “ includes ” and “ include ”) or “ containing ” ( and any form of containing , such as “ contains ” and “ contain ”) are inclusive or open - ended and do not exclude additional , unrecited elements or method steps . the term “ or combinations thereof ” as used herein refers to all permutations and combinations of the listed items preceding the term . for example , “ a , b , c , or combinations thereof ” is intended to include at least one of : a , b , c , ab , ac , bc , or abc , and if order is important in a particular context , also ba , ca , cb , cba , bca , acb , bac , or cab . continuing with this example , expressly included are combinations that contain repeats of one or more item or term , such as bb , aaa , mb , bbc , aaabcccc , cbbaaa , cababb , and so forth . the skilled artisan will understand that typically there is no limit on the number of items or terms in any combination , unless otherwise apparent from the context . all of the compositions and / or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure . while the compositions and methods of this invention have been described in terms of preferred embodiments , it will be apparent to those of skill in the art that variations may be applied to the compositions and / or methods and in the steps or in the sequence of steps of the method described herein without departing from the concept , spirit and scope of the invention . all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit , scope and concept of the invention as defined by the appended claims . lototsky , m . v . ; yartys , v . a . ; klochko , ye . v . ; starovoitov , r . i . ; azhazha , v . m . ; v &# 39 ; yugov , p . n . journal of alloy and compounds , 404 - 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