Radiofrequency attenuator and method

Abstract

Radiofrequency attenuator and method. The attenuator includes a pair of transparent windows. A chamber between the windows is filled with molten salt. Preferred molten salts include quarternary ammonium cations and fluorine-containing anions such as tetrafluoroborate (BF 4 − ), hexafluorophosphate (PF 6 − ), hexafluoroarsenate (AsF 6 − ), trifluoromethylsulfonate (CF 3 SO 3 − ), bis(trifluoromethylsulfonyl)imide ((CF 3 SO 2 ) 2 N − ), bis(perfluoroethylsulfonyl)imide ((CF 3 CF 2 SO 2 ) 2 N − ) and tris(trifluoromethylsulfonyl)methide ((CF 3 SO 2 ) 3 C − ). Radicals or radical cations may be added to or electrochemically generated in the molten salt to enhance the RF attenuation.

What is claimed is:  
     
         1 . A radiofrequency attenuator, comprising in combination: 
 (a) a substantially transparent container; and    (b) molten salt sealed inside said container.    
     
     
         2 . The radiofrequency attenuator of  claim 1 , wherein said transparent container comprises, in combination: 
 (a) a first transparent window;    (b) a second transparent window; and    (c) a chamber for receiving molten salt between said first transparent window and said second transparent window.    
     
     
         3 . The radiofrequency attenuator of  claim 2  wherein said chamber comprises a chamber width of about 50-5000 microns between said first transparent window and said second transparent window.  
     
     
         4 . The radiofrequency attenuator of  claim 2 , wherein said chamber comprises a chamber width of about 50-500 microns between said first transparent window and said second transparent window.  
     
     
         5 . The radiofrequency attenuator of  claim 2 , wherein said molten salt comprises at least one cation selected from the group consisting of lithium cation and quarternary ammonium cations.  
     
     
         6 . The radiofrequency attenuator of  claim 2 , wherein said quarternary ammonium cations are selected from the group consisting of pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, thiazolium, oxazolium, triazolium, tetraalkylammonium, and N-methyl morpholinium.  
     
     
         7 . The radiofrequency attenuator of  claim 5 , wherein said quarternary ammonium cations comprise the formula [(CH 3 CH 2 ) 3 N(Ri)] + , wherein R 1  is alkyl having 2-10 carbons; or comprise the formula [(CH 3 ) 2 (CH 3 CHCH 3 )N(R 2 )] + , wherein R 2  is alkyl having 2-10 carbons; or comprise the structural formula  
       
         
           
           
               
               
           
         
       
       wherein R 3  is alkyl having 2-10 carbons;  
       or comprise the structural formula  
       
         
           
           
               
               
           
         
       
       wherein R 4  is alkyl having 2-10 carbons.  
     
     
         8 . The radiofrequency attenuator of  claim 2 , wherein said molten salt comprises at least one anion selected from the group consisting of tetrafluoorborate (BF 4   − ), hexafluorophosphate (PF 6   − ), hexafluoroarsenate (AsF 6   − ), trifluoromethylsulfonate (CF 3 SO 3   − ), bis(trifluoromethylsulfonyl)imide ((CF 3 SO 2 ) 2 N − ), bis(perfluoroethylsulfonyl)imide ((CF 3 CF 2 SO 2 ) 2 N − ) and tris(trifluoromethylsulfonyl)methide ((CF 3 SO 2 ) 3 C − ).  
     
     
         9 . The radiofrequency attenuator of  claim 2 , further comprising means for applying voltage between said first transparent window and said second transparent window.  
     
     
         10 . The radiofrequency attentuator of  claim 2 , further comprising radicals sealed inside said chamber with said molten salt.  
     
     
         11 . The radiofrequency attenuator of  claim 10 , wherein said radicals are soluble in said molten salt.  
     
     
         12 . The radiofrequency attenuator of  claim 10 , wherein said radicals are insoluble in said molten salt.  
     
     
         13 . The radiofrequency attenuator of  claim 10 , wherein said radicals are selected from the group consisting of galvinoxyl radicals, trityl radicals, nitroxide radicals, nitronyl nitroxide radicals, semiquinone radicals, diaminobenzene radicals, ferrocenyl radicals, viologen radical cations, lanthanide radicals, and metal oxide radicals.  
     
     
         14 . The radiofrequency attenuator of  claim 2 , wherein said first transparent window and said transparent window comprise ITO.  
     
     
         15 . A method for attenuating radiofrequency radiation, comprising filling a substantially transparent container with molten salt and positioning the container in the path of radiofrequency radiation.  
     
     
         16 . The method of  claim 15 , wherein the transparent container comprises in combination: 
 (a) a first transparent window;    (b) a second transparent window; and    (c) a chamber for receiving molten salt between said first transparent window and said second transparent window.    
     
     
         17 . The method of  claim 16 , wherein the chamber comprises a chamber width of about 50-5000 microns between the first transparent window and the second transparent window.  
     
     
         18 . The method of  claim 16 , wherein the chamber comprises a chamber width of about 50-500 microns between said first transparent window and said second transparent window.  
     
     
         19 . The method of  claim 16 , wherein the molten salt comprises at least one cation selected from the group consisting of lithium cation and quarternary ammonium cations.  
     
     
         20 . The method of  claim 16 , wherein the quarternary ammonium cations are selected from the group consisting of pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, thiazolium, oxazolium, triazolium, tetraalkylammonium, and N-methyl morpholinium.  
     
     
         21 . The method of  claim 19 , wherein the quarternary ammonium cations have the formula [(CH 3 CH 2 ) 3 N(R 1 )] + , wherein R 1  is alkyl having 2-10 carbons; or have the formula [(CH 3 ) 2 (CH 3 CHCH 3 )N(R 2 )] + , wherein R 2  is alkyl having 2-10 carbons; or have the structural formula  
       
         
           
           
               
               
           
         
       
       wherein R 3  is alkyl having 2-10 carbons;  
       or have the structural formula  
       
         
           
           
               
               
           
         
       
       wherein R 4  is alkyl having 2-10 carbons.  
     
     
         22 . The method of  claim 16 , wherein the molten salt comprises at least one anion selected from the group consisting of tetrafluoroborate (BF 4   − ), hexafluorophosphate (PF 6   − ), hexafluoroarsenate (AsF 6   − ), trifluoromethylsulfonate (CF 3 SO 3   − ), bis(trifluoromethylsulfonyl)imide ((CF 3 SO 2 ) 2 N − ), bis(perfluoroethylsulfonyl)imide ((CF 3 CF 2 SO 2 ) 2 N − ) and tris(trifluoromethylsulfonyl)methide ((CF 3 SO 2 ) 3 C − ).  
     
     
         23 . The method of  claim 16 , wherein the transparent container further comprises means for applying voltage between said first transparent window and said second transparent window.  
     
     
         24 . The method of  claim 16 , further comprising radicals sealed inside the chamber with the molten salt.  
     
     
         25 . The method of  claim 24 , wherein the radicals are soluble in the molten salt.  
     
     
         26 . The method of  claim 24 , wherein the radicals are insoluble in the molten salt.  
     
     
         27 . The method of  claim 24 , wherein the radicals are selected from the group consisting of galvinoxyl radicals, trityl radicals, nitroxide radicals, nitronyl nitroxide radicals, semiquinone radicals, diaminobenzene radicals, ferrocenyl radicals, viologen radical cations, lanthanide radicals, and metal oxide radicals.  
     
     
         28 . The method of  claim 16 , wherein the first transparent window and the second transparent window comprise ITO.