b'P ROVING THE P RINCIPLEHeath went on to standardize the way measuring cross-sections, a term section as a function of neutron energy.measurements were made. He prepared originating from the graphic method (This total cross section is the sum ofa catalog containing the gamma energy used to depict the process.the absorption and scattering cross sec-spectrum and half-lives of hundreds of tions.) In the case of samples that scat-radionuclides. Phillips published the To complicate matters, the probabilities ter the neutrons, the scientists measuredfirst edition in 1958 and several there- of absorption or scattering are different the angular distribution of the neutronsafter. The Blue Book, as the catalog depending on the energy of the neu- and the energy difference between inci-was known, made it possible for trons. The group selected the neutron dent and scattered neutrons with a slowresearchers elsewhere to profile and energy with an instrument called a neu- neutron velocity selector developed byidentify mysterious elements without tron crystal spectrometer. Another Dr. Brugger. Brugger also developed aspending tedious weeks or months instrument was the fast neutron chopper technique to expose samples under mil-doing so. It was a valuable contribution and time-of-flight spectrometer. Here, it lions of atmospheres of pressure to theto the worlds store of information was possible to chop the beam of neutron beams of the MTR. 11about the nature of matter. The catalog neutrons into pulses as short as a mil-continued in use over forty years later. 10 lionth of a second. These pulses would The work opened a new frontier. Nothen spread out in time as the neutrons, one previously had such access to theAnother group of physicists under the with different velocities, traveled down exotic radioactive nuclides that the sci-leadership of Dr. Robert Brugger took a long flight path to the detector array. entists studied at the MTRor such afull advantage of the MTRs high neu- Whenever the scientists put a sample in team of chemists and physicists makingtron flux and its beam holes. When the beam, some of the neutrons were the most of the opportunity. The find-unobstructed by shielding, a beam of removed. From the ratio of the sample- ings were of incalculable value in theneutrons streaming out of the reactor in to sample-out detector signals, the design of reactors. If fertile uranium (orwas a tool useful for exploring the scientists could calculate the total cross thorium) were to be packed around thenature of matter at the level of thenucleus. Although scientists elsewherehad access to spectrometers and otherinstruments, they did not have accessto the neutron flux of the MTR or theavailability of hot samples producedwithin the MTR. The basic idea was tobombard isotopes with neutrons. Theatomic nuclei sometimes absorb theseneutrons, sometimes bounce them off.Bruggers group studied these interac-tions and calculated the probabilitiesfor each reaction. This was calledThe MTR is all but hidden by experimentalapparatus. Samples are being irradiated throughbeam port at right. Another port is being preparedfor an experiment near stile-like stairway. Boxescontain paraffin and other shielding materials. Rackof handling tools stands ready at balcony level.INEEL 61-20561 1 0'