Cyclotron nuclear reactions

A similar experiment was reported by RJ. Dougan et al. [90], A set-up called Qn-line Separation and Condensation AppaRatus (OSCAR) was installed at the LBNL 88-Inch Cyclotron. Nuclear reaction products were collected with a KQ aerosol gas-jet and were transported from the target chamber to the OSCAR set-up where 02 was added. The aerosol particles were destroyed on a hot quartz wool plug and the formation of tetroxides occurred at a temperature of 650°C. Non volatile reaction products were retained on the quartz wool plug whereas the volatile tetroxides were swept by the carrier gas flow to a condensation chamber, where they were deposited on a Ag disk, which was cooled with liquid N2. An annular Si... 

The sources used in Ni Mossbauer work mainly contain Co as the parent nuclide of Ni in a few cases, Cu sources have also been used. Although the half-life of Co is relatively short (99 m), this nuclide is much superior to Cu because it decays via P emission directly to the 67.4 keV Mossbauer level (Fig. 7.2) whereas Cu ti/2 = 3.32 h) decays in a complex way with only about 2.4% populating the 67.4 keV level. There are a number of nuclear reactions leading to Co [4] the most popular ones are Ni(y, p) Co with the bremsstrahlung (about 100 MeV) from an electron accelerator, or Ni(p, a) Co via proton irradiation of Ni in a cyclotron. 

Lawrencium - the atomic number is 103 and the chemical symbol is Lr. The original chemical symbol was proposed as Lw but it was changed because W is an unusual occurrence in many languages and it is a cumbersome spoken word. The name derives from the American physicist Ernest O. Lawrence , who developed the cyclotron. Credit for the first synthesis of this element in 1971 is given jointly to American chemists from the University of California laboratory in Berkeley, California under Albert Ghiorso and the Russian scientific team at the JINR (Joint Institute for Nuclear Reactions) lab in Dubna, Russia under Georgi N. Flerov, after a series of preliminary papers presented over a decade. The longest half-life associated with this unstable element is 3.6 hour Lr. 

Unnilseptium, or bohrium, is artificially produced one atom at a time in particle accelerators. In 1976 Russian scientists at the nuclear research laboratories at Dubna synthesized element 107, which was named unnilseptium by lUPAC. Only a few atoms of element 107 were produced by what is called the cold fusion process wherein atoms of one element are slammed into atoms of a different element and their masses combine to form atoms of a new heavier element. Researchers did this by bombarding bismuth-204 with heavy ions of chromium-54 in a cyclotron. The reaction follows Bi-209 + Cr-54 + neutrons = (fuse to form) Uns-262 + an alpha decay chain. 

Fluorine-18 is readily available from cyclotrons by using a wide variety of nuclear reactions. The most common methods to produce F are given in Table 4. They will not be discussed here as more elaborated details can be... 

Neptunium, the first transuranium element, was discovered hy E. M. McMdlan and P. H. Ahelson in 1940 in Berkeley, California. It was produced in the cyclotron in a nuclear reaction by bombarding uranium-238 with neutrons. An isotope of mass 239 and atomic number 93 and ti/2 of 2.4 days was produced in this reaction. Neptunium-237, the longest-lived alpha-emitter with half-life 2.14x10 years, was discovered two years later in 1942 by Wahl and Seaborg. The new element was named after the planet Neptune, the planet next to Uranus in the solar system. 

Plutonium is produced from natural uranium which is a mixture of nonfis-sionable uranium-238 (99.3%) and fissionable uranium-235(0.7%). The first synthesis of this element was in a cyclotron generating plutonium in microgram quantities. The isotope Pu-239 can be produced in much larger quantities in a nuclear reactor, either a conventional thermal reactor or a breeder type reactor by neutron bombardment of uranium- 238. The nuclear reactions are shown below. 

For the 0(p,n) F nuclear reaction, the oxygen-18 target material normally consists of highly enriched (>95%) liquid [ 0]water, but [ 0]dioxygen gas has been used as well [19,37]. Appropriate cyclotron targetry allows a batch production of several Curies of [ F]fluorine in a single irradiation of a few hours. While the theoretical specific radioactivity of carrier-free fluorine-18 is 1.7 x 10 ... 

Production of Sr-82. An important consideration in the development of radioisotope generators is the availability, cost, and radionuclidic purity of the long-lived parent. In the case of Sr-82, the 25 day radionuclide is needed in 100-200 mCi amounts in order to provide adequate elution yields of Rb-82 from one loading of Sr-82 every three months. Initially the Sr-82 for the generator was produced at the Lawrence Berkeley Laboratory (LBL) 88-inch cyclotron by the Rb-85 (p,4n) Sr-82 nuclear reaction (12). However, because of the long irradiation time required to produce... 

Irradiation with charged particles accelerated in a cyclotron, while eliminating the problem of long-lived silver isotopes caused by the different nuclear reactions involved, is not feasible for any large-scale study because of the cost involved. Unlike a nuclear reactor, where numerous different samples can be irradiated simultaneously, only a single sample can be irradiated using a cyclotron beam. 

Alpha particles from radioactive samples, or He2+ ons accc cralc(l n a cyclotron, may be used to bring about other nuclear reactions. For example, they may bombard a beryllium metal target ... 

As indicated above, a combination of reactor and cyclotron irradiations is used to prepare most radionuclides. While many of these radionuclides are available commercially, some are not. In addition, nuclear structure, nuclear reactions, and heavy-element research require accelerator or reactor irradiations to produce short-lived nuclei or to study the dynamics of nuclear collisions, and so on. One of the frequent chores of radiochemists is the preparation of accelerator targets and samples for reactor irradiation. It is this chore that we address in this section. 

F was produced by irradiating H2160 water target in a cyclotron in the 160(3Fle, p)18F nuclear reaction. 

An interesting concept that must always be taken into account in cyclotron-produced radionuclides is the saturation activity characteristic of each target and each nuclear reaction. The saturation activity is the activity of the radionuclide in which the secular equilibrium is obtained between the activity produced in the target and the disintegration of the radioisotope. The activity produced at a target can be calculated by the equation... 

Note Most common reactions used in small cyclotrons are bolded. Different energies of the incident particle are needed for the different nuclear reactions... 

The only radioi.sotope of gallium that is prc.sently used is gallium-67, which is produced in a cyclotron by proton bombardment of a zinc metal target by a " Zn(p.2n) Ga nuclear reaction. Gallium-67 U n = 78.2 hours) decays by electron... 

Element 106, named seaborgium to honor Glen Seaborg, was created in 1974 by the Flerov Laboratory of Nuclear Reactions in Dubna, in the Soviet Union, and at the Lawrence Berkeley and Livermore Laboratories, in the United States. Seaborgium isotopes are created using a cyclotron and can exist from about 0.9 seconds up to about 20 seconds before they decay into other elements. This is enough time to determine the properties of seaborgium and to confirm that it qualifies as an element. 

He attended the University of California at Berkeley as a national research fellow working in the field of molecular beams, in particular the measurement of the magnetic moment of the proton by a molecular beam method. He became a member of the team at the radiation laboratory under Professor E.O. Lawrence, studying nuclear reactions and their products and helping design and construct cyclotrons. 

Figure 26-8 A beam of protons (bright blue stream) from a cyclotron at the Argonne National Laboratory. Nuclear reactions take place when protons and other atomic particles strike the nuclei of atoms.

---