Patent Number: 
Section: claims

1. A fluorescent X-ray spectroscope comprising: a source of X-rays having an X-ray generating point;  an X-ray shielding plate having an entrance window to emit X-rays from the X-ray generating point;  a first elongated glass tube having a first aperture extending the length of the first glass tube for guiding the X-rays;  a sample stage aligned with one end of the first glass tube to receive the X-rays; and  a first protective X-ray tube positioned about the first glass tube and extending substantially along an intermediate length of the first glass tube to block off-axis X-rays that are not aligned with the first aperture of the first glass tube. 2. The invention of  claim 1  further including a mount base for holding the first protective X-ray tube. claim 1 3. The invention of  claim 2  further including a second elongated glass tube with a second aperture of a size different than the first aperture and a second protective X-ray tube positioned about the second glass tube and held in the mount base. claim 2 4. The invention of  claim 3  wherein the mount base includes an X-ray shielding tube extending upward from the mount base to the X-ray shielding base. claim 3 5. The invention of  claim 4  wherein the respective first and second glass tubes extend within the X-ray shielding tube and the first and second protective X-ray tubes extend below the X-ray shielding tube. claim 4 6. The invention of  claim 5  wherein the entrance window has a diameter of r 1 , the first protective X-ray tube has an inside diameter of r 2 , x 1  is a distance from an X-ray generating point of the source of X-rays to the X-ray shielding plate and x 2  is a distance from the X-ray generating point to an input end of the first protective X-ray tube wherein the following condition applies: claim 5 r 1 /x 1  less than r 2 /x 2 7. An X-ray shielding mechanism for off-axis X-rays provided with an X-ray cartridge comprising: r 1 /x 1  less than r 2 /x 2  an X-ray source which radiates X-rays;  a glass X-ray guide tube with an inner peripheral surface into which the X-rays are introduced;  an X-ray shielding plate made of metal and having a window for introducing X-rays into the X-ray guide tube, the shielding plate is disposed on an input end of the X-ray guide tube, and  a metallic protective pipe which has a predetermined length extending from the side of the input end at a predetermined distance from the X-ray source to the side of the end, from which the X-rays are emitted, and which is disposed outside of the X-ray guide tube whereby the X-rays which pass through the entrance window and are transmitted from a side surface of the X-ray guide tube can be blocked and satisfying the following condition:  wherein r 1  is a diameter of the entrance window of the X-ray shielding plate, x 1  is a distance from an X-ray generation point of the X-ray source to the X-ray shielding plate, x 2  is a distance from the X-ray generation point to an input end of the protective pipe and r 2  is the inside diameter of the protective pipe. 8. An X-ray shielding mechanism of  claim 7  wherein the X-ray cartridge has a plurality of X-ray guide tubes and a mount base which supports these X-ray guide tubes and switches the X-ray guide tubes relative to the X-ray source. claim 7 9. An X-ray shielding mechanism of  claim 8  wherein the mount base supports the metallic X-ray shielding pipe positioned on the outside of the X-ray guide tube and the X-ray shielding plate positioned on the side of the input end of the X-ray guide tube is supported by an X-ray shielding pipe. claim 8 10. In an X-ray analytical instrument for applying and analyzing the consequence of X-rays applied to a sample, the improvement of: r 1 /x 1  less than r 2 /x 2  an elongated glass guide tube for guiding X-rays to the sample from a source of X-rays; and  an outer metallic tube of sufficient density and length to block X-rays extending about the elongated glass guide tube whereby off-axis X-rays transmitted through an outer surface of the guide tube are blocked, wherein the X-ray analytical instrument includes an entrance window in an X-ray shielding plate having a diameter r 1 , the metallic tube has an inside diameter of r 2 , x 1  is a distance from an X-ray generating point of an X-ray source to the X-ray shielding plate and x 2  is a distance from the X-ray generating point to an input end of the metallic tube wherein the following condition applies: 11. In an X-ray analytical instrument for applying and analyzing the consequence of X-rays applied to a sample, the improvement of an elongated glass guide tube for guiding X-rays to the sample from a source of X-rays; and r 1 /x 1  less than r 2 /x 2 .  an outer stainless steel tube of sufficient density and length to block X-rays extending about the elongated glass guide tube whereby off-axis X-rays transmitted through an outer surface of the guide tube are blocked, wherein the X-ray analytical instrument includes an entrance window in an X-ray shielding plate having a diameter r 1 , the stainless steel tube has an inside diameter of r 2 , x 1  is a distance from an X-ray generating point of an X-ray source to the X-ray shielding plate and x 2  is a distance from the X-ray generating point to an input end of the stainless steel tube wherein the following condition applies: