A coaxial probe comprising: an inner rod ; an outer shell circumferentially enclosing the inner rod ; a plurality of U-shaped spacers , wherein the U-shaped spacers each comprise a spacer opening such that the U-shaped spacers are held in position by friction; wherein the inner rod has a body diameter and comprises a plurality of stepped down zones having a stepped diameter smaller than the body diameter; wherein the plurality of U-shaped spacers are frictionally attached to the stepped down zones ; and are further restricted to the stepped down zones because the body diameter is greater than the stepped diameter; wherein the outer shell comprises a plurality of perforations through which a fluid can flow; characterized in that each spacer opening is adapted to spread open when the spacer opening is placed on the inner rod and to snapp onto the inner rod such that the U-shaped spacers are held in the position by the friction; wherein a plurality of U-shaped spacers are snapped onto the inner rod at any unprepared spot to be hold in position by friction, wherein the coaxial probe further comprises a plurality of crimpings in the outer shell and positioned over the U-shaped spacers to thereby lock the U-shaped spacers in place, and a plurality of fasteners passing through the outer shell and into at least one of the U-shaped spacers ; wherein the coaxial probe further comprises an additional inner rod attached end-to-end with the inner rod , an additional outer shell attached end-to-end with the outer shell , wherein the inner rod , outer shell , additional inner rod , and additional outer shell comprise threaded ends , wherein the threaded ends attach the inner rod to the additional inner rod and attach the outer shell to the additional outer shell ; and wherein the inner rod and the outer shell , the additional inner rod , the additional outer shell are stainless steel, or an alloy comprising at least 62% nickel and 27% copper; or a superalloy. an inner rod ; an outer shell circumferentially enclosing the inner rod ; a plurality of U-shaped spacers , wherein the U-shaped spacers each comprise a spacer opening such that the U-shaped spacers are held in position by friction; wherein the inner rod has a body diameter and comprises a plurality of stepped down zones having a stepped diameter smaller than the body diameter; wherein the plurality of U-shaped spacers are frictionally attached to the stepped down zones ; and are further restricted to the stepped down zones because the body diameter is greater than the stepped diameter; wherein the outer shell comprises a plurality of perforations through which a fluid can flow; characterized in that each spacer opening is adapted to spread open when the spacer opening is placed on the inner rod and to snapp onto the inner rod such that the U-shaped spacers are held in the position by the friction; wherein a plurality of U-shaped spacers are snapped onto the inner rod at any unprepared spot to be hold in position by friction, wherein the coaxial probe further comprises a plurality of crimpings in the outer shell and positioned over the U-shaped spacers to thereby lock the U-shaped spacers in place, and a plurality of fasteners passing through the outer shell and into at least one of the U-shaped spacers ; wherein the coaxial probe further comprises an additional inner rod attached end-to-end with the inner rod , an additional outer shell attached end-to-end with the outer shell , wherein the inner rod , outer shell , additional inner rod , and additional outer shell comprise threaded ends , wherein the threaded ends attach the inner rod to the additional inner rod and attach the outer shell to the additional outer shell ; and wherein the inner rod and the outer shell , the additional inner rod , the additional outer shell are stainless steel, or an alloy comprising at least 62% nickel and 27% copper; or a superalloy. <EOS>