A brief review of known mechanisms for formation of PCDD/Fs is presented. In this study, various lignin preparations and low molecular weight phenols that can be derived from lignin were chlorinated with or without unbleached pulp present to gain information on the formation of chlorinated dioxins and furans during pulp bleaching. Chlorination of lignin produced results similar to chlorination of unbleached pulp in terms of amounts of TCDD/Fs and isomer patterns. Spiking pulp with guaiacol (2-methoxyphenol), 2,4,5-trichlorophenol, and 4,5-dichlorocatechol all increased the levels of chlorinated dioxins, but suppressed formation of the furans. Coupling of chlorophenols does not appear to be a major pathway for formation of the 2378-TCDD and 2378-TCDF during pulp bleaching.

A detailed study of a separated-magnet two-stage cyclotron has been made. For elements heavier than S, ions are preaccelerated by a 700 keV Cockroft-Walton and then injected into the first stage (lower gap) of the cyclotron. After acceleration, extraction and stripping (from charge Q to 4Q) they are returned to the center of the second stage (upper gap, whose center line is 15 inches above that of...

Negative hydrogen ions are accelerated at a fixed magnetic field. The energy of an extracted beam is determined by the radius of a stripping foil and its azimuth and radius determine the exit point of the beam from the cyclotron. The exit points can be adjusted so that an auxiliary magnet causes the various extracted beams to enter a common beam transport system. Since February, 1966, external beams whose energy is variable from 25 to 50 MeV have been produced by the above means at UCLA and the University of Manitoba. While this is primarily a report on the UCLA system and its performance, special features of the Manitoba system are presented.

An FFAG accelerator has advantages for use as a “meson factory”, for the production of intense pion beams. The greatest advantage is the flexibility in duty factor arising from beam stacking. Beams can be brought onto targets with duty factors varying from 10−6 to unity, for use with different detectors. A conceptual design of an FFAG accelerator has been carried out. It is estimated that this design will accelerate more than 1015 protons per second to an energy of 720 MeV.

The design and operation of the U.C.L.A. 50 Mev cyclotron is described. The magnetic field is presented in a series of graphs and orbit calculations on beam stability are given. The results of experimental observations and measurements on the internal beam include beam intensity graphs and photographs, piots of / nu /sub z/ and nu /sub r/ from r.f. knockout measurements, beam intensity as a function of dee voltage, and radial oscillation amplitude of the beam. Because of iack of shielding, the beam has been restricted to 2 mu a of 50 Mev protons by use of a 5% duty cycle. An increased intensity is expected when a puller electrode is used at the source. The tuning up of the beam by means of the eight circular coils for trimming the magnetic field has been found to be quite simple in practice. Efforts to get an external beam are now proceeding in the permanent shielding vault. (auth)

The precision in the field measurements necessary for satisfactory operation of this cyclotron is calculated. The Hall plate detectors are described. The various methods of field measurement used to give the desired precision are presented.

Two model constant-frequency cyclotrons based on the principle of L. H. Thomas, as extended by David L. Judd, are described. Both accelerated electrons to speeds of half that of light in magnetic fields of three-fold azimuthal periodicity. Three 60°-wide wedge-shaped electrodes, driven 120° out of phase, provided an energy gain per revolution of 3 eV0, where V0 is the peak electrode-to-ground voltage. Electrons were accelerated to 75 kv with V0=23 v, implying a minimum of one thousand revolutions in the cyclotron. The beam reached full energy without axial loss and it was demonstrated that essentially all of the circulating current will emerge from this type of accelerator without the use of additional deflecting systems. The success of this development program has shown the feasibility of a high-current, high-energy cyclotron based on the Thomas principle.

The differential cross section in the center-of-mass system for 12.4-Mev proton-proton scattering has been determined in the neighborhood of a scattering angle of 90\ifmmode^\circ\else\textdegree\fi{}. A photographic technique was used with a camera having cylindrical symmetry. The function $f(E)$ as defined by Bethe has been calculated for each of the three cross-section runs which were made. The average value of $f(E)$ as determined by the experiment agrees closely with the value predicted by a linear extrapolation from the results below 4 Mev.

The experimental development of the phase stability principle as applied to the 37-inch f-m cyclotron is discussed. The ions were required to pass through an over-all radial decrease in magnetic field of 13 percent. Some theoretical estimates of the yield vs. modulation frequency are given and these were found to be in satisfactory agreement with the experimental results. It is found that some of the ions emerge as late as four or five modulation cycles after their initial acceleration. Observations were made of the time of flight of the ions and evidence was found of the actual phase oscillations in the shape of the ion current patterns. The ion current received by a probe at different radii and different pressures using a pulsed source was analyzed, and indicates a considerable loss of beam at dee voltages less the 60 kev. The data confirm the variation of ion beam loss as the reciprocal of the square of the ion energy and extend the validity of this relation to 600 kev for deuterons. The variation of ion current with dee voltage is quite steep. A deflected beam amounting to 10 percent of the circulating current was obtained, taking advantage of the precessional motion of the ion orbits. Circulating ion currents of 3 \ensuremath{\mu}a of 7.5-Mev deuterons and 2 \ensuremath{\mu}a of 14.6-Mev protons were obtained.

The scattering of 14.5 Mev protons by protons has been studied by using a coincidence counting method. The 14.5 Mev protons were obtained from the 37-inch synchrocyclotron at Berkeley. The measurements of the differential scattering cross section are absolute and extend from 10\ifmmode^\circ\else\textdegree\fi{} to 45\ifmmode^\circ\else\textdegree\fi{}. The accuracy was not high, about ten percent, because the pulsed nature of the synchrocyclotron beam introduced a large background of accidental counts. At small angles the scattering is significantly larger than that predicted by $S$ wave scattering only. This indicates the effect of $P$ wave scattering such as that due to a repulsive potential well. The results are not inconsistent with those found at 8 and 10 Mev.

A detailed study of a separated-magnet two-stage cyclotron has been made. For elements heavier than S, ions are preaccelerated by a 700 keV Cockroft-Walton* and then injected into the first stage (lower gap) of ttir cyclotron. After acceleration, extraction and stripping (from charge Q to 4Q) they are returned to the center of the second stage (upper gap, whose center line is 15 inches above that of tile lower gap) and further accelerated. For ions lighter than S, preacceleration takes place in a small cyclotron and the ions are injected directly into the second stage of the large cyclotron. Protons may be accelerated from 4 to 200 MeV , 3He from 12 to 630 McV and lJ from 620 to 2110 ?ZeV. The nmgnit~!dt~ of extcrcnl beams of heavy ions is limited by heating and sputtering of tile electrostatic deflcctor i'xtrnction system. 'The turn separation for uranium ior.s at the final radius is 16 mm, so extractier. efFirienci?s above 902 should be possible. A t 9 0 % it is estimated that 1 particle microampere of uranium ions will be obtained.