Synchrotron

We investigate a magnetized plasma in which injected high-energy γ-rays annihilate on a soft photon field that is provided by the synchrotron radiation of the created pairs. For a very wide range of magnetic fields, this process involves γ-rays between 0.3 GeV and 30 TeV. We derive a simple dynamical system for this process, analyze its stability to runaway production of soft photons and pairs, and find conditions for it to automatically quench by reaching a steady state with an optical depth to photon-photon annihilation larger than unity. We discuss applications to broadband γ-ray emitters, in particular supermassive black holes. Automatic quenching limits the γ-ray luminosity of these objects and predicts substantial pair loading of the jets of less active sources.

It was originally expected that the winding operation would require about 6 months, but the delay was caused largely by unreliable delivery and quality of the vendor furnished bakelite coil spacers for the third and fourth quadrants, and the diversion of manpower and cranes to classified work. The The coil consists of 176 turns of 1-7/8 inch diameter stranded copper cable, 26 miles long weighing 347 tons and wound on a.l08 ft. o.d. and 86ft. i.d.

Magnet
The magnet test without pole pieces is proceeding and it is expected that the pulsed power from the generators will be connected to the coils b.y the end of July. The oil pumps which are belt-driven by the ~ shafts have been installed to provide bearing lubrication while the machine is coasting in case of power failure, and the motor-generators have been run satisfactorily on open-circuit to test the bearings and controls. The magnet model tests for determining the final pole tip outline are continuing. Casting of the pole tip stanchions has been postponed pending model test results of the required shaped pole profile. Mare Island Shipyard has submitted several more nickel cast-iron samples of the pole tip stanchion material with lower magnetic permeability, and the permeability measurements are continuing. Since the Brookhaven tests have indicated that there is no possible need for a 2 x 6 ft. aperture at UCRL, the pole base length will be shortened to 66 inches, the . length of the pole tips with the 1 x 4 ft. aperture, in order to save steel. The pole face windings will consist of 5/16 inch o.d. x 1/16 inch wall copper tubing at 3 inch centers to provide ample capacity (several hundre4 amperes) for correcting the field shape~ * Previous report UGRL-1883 (No. 110) -3-Vacuum System UCRL-1904 UNCLASSIFIED The first straight tank will probably be completed by October 2lo Two transition tanks should be completed by August lo Sufficient material for the first curved tank should be delivered to UCRL by August l5o The • filler frame (for supporting the vacuum tank in the area left unsupported by the smaller pole tips) has been redesigned to reduce eddy current heatingo Range Energy Relations for Multiply Charged Particleso It is well known that the range-energy relations of heavy particles penetrating matter, aside from a correction for electron pick-up near the end of the range, are related as followsg In this relation T is the kinetic energy~ M the mass, Z the charge, and R the residual range., Using disintegration products of high energy reactions in the 184-inch cyclotron, the range ene-rgy relation for Li and B isotopes have now been studi.ed o The correction to the range arising from electron pick-up has been evaluatedo It appears that the range extension in emulsion can be esti= mated with good accuracy from the formula 6R = Oo6A microns, where A is the mass numbero Physical AnaLysis of High Energy Disintegration Productso A comparison of the disintegration products of C and Be bombarded b.1 330 Mev protons indicates that from each nucleus the alpha particle is the most abundant producto Except for tritium and deuterium, the proportions of other products are somewhat the same from the two nucleio Be yields two or three times as much tritium as Co One result which appears remarkable is that large clusters of nucleons, BS for example, may absorb the whole momentum of the proton yet not be torn apart., other Projectso A number of other projects are active, but no new results have been obtained during the present report period.,

UCRL-1904 UNClASSIFIED
During the report period there was a run at the 184-inch cyclotron using the meson cloud chamber for the study of rr-minus capture in heli~ Film from the run shows the background situation to be greatly improved, and the information from this run will make possible elimination of the greater part of the remaining backgroundo The experiment on photodisintegration of the deuteron using a rectangular cloud chamber in the 322 million volt gamma ray beam from the synchrotron is being continued.. Considerable film has been exposed in explorator,y runs to determine the frequency of events which may be expectedo There was a second run using the ten-atmosphere cloud chamber at the 184-inch cyclotron for a study of high energy n-p scatteringo One day's film was obtained and a number of events have been found, though the pulse strength of the cyclotron was extremely variable throughout the run ..
The rectangular diffusion chamber for the study of rr-minus scattering on deuterium has been made.to operate successfully with the high pressure cylinder in place inside the chamber ..
The development of an ionization chamber for the study of photQao disintegration of helium 3 is continuingo The control and cable systems for operating cloud chambers in conjunction with the linear accelerator have been substantially completed.. Modification of the horizontal Helmholz coils for use in conjunction with the linear accelerator has been carried out ..

Annihilation of Positrons and Electrons in Flight
The experiment on the annihilation of positrons and electrons in flight was continued with a three day run on the synchrotron.. This time was used to gain better statistics for the energies 50 Mev~ 100 ~v~ and 200 Mev, using the original apparatus and primarily the low Z targets of Be and LiHo The positron annihilation in flight cross section as determined experimentally agreed with the theoretical cross section with a statistical error of ± 15 percent at the three energies 200~ 100, and 50 Mevo There is a factor of three difference in the cross section between 50 and 200 Mev, and this energy dependence was observed., The electrons in low Z elements (Be and LiH) at 200 Mev did not "disappear 11 by a factor 1/lOth of the positron annihilation cross section, which is l/60th the disappearance cross section of the two events observed in nuclear emulsion by Gilbert et alo The disappearance of electrons in Ag at 200 Mev corresponded to 1/2 the nuclear emulsion cross section and at least a factor of 2 of this cross section could be ascribed to bremsstrahlung ..

UCRL-1904 UNC IASS IFIED
It is tentatively proposed that the two disappearances observed by Gilbert, et alo 9 were positron annihilations in flight, namely that the magnetic field was reversed., This error has definitely shown up on a set of plates exposed at a lower energyo The larger annihilation cross section ob-served9 (1/J event would be expected whereas 2 were seen) 9 can be roughly ascribed to the fact that some of the 200 Mev positrons radiated a large fraction of their energy in the emulsion and then their annihilation cross section would increase as 1/Eo A brief but unrewarding search was made at the end of the run, to observe the annihilation gammas in coincidence with the disappearance of a positrono The trouble was largely that too low an energy of positrons was used so that scattering spread the forward annihilation quanta·over too large a solid angleo It is hoped that these gamma rays can be observed during a one~day run in the near futuree Frotoo-?roton Scattering at Reduced Energies (16o to 250 M §v) In the last run the energy of the proton beam emerging from the lithium attenuator was lower than expectedo This has been explained, in that the can surrounding one of the pieces of lithium was not tight, and over a period of months oxidation has greatly increased the stopping power of this absorber Another run is expected within a few weekso Total Proton-Proton Scattering Cross Section (345 Mev) Several serious leaks in the large liquid hydrogen target have been foundo These have necessitated considerable reworking a This is now 'being: done in the shopso neutron Proton Scattering at Small Angles (10° to 30°v 90 Mev and 270 Mev) Equipment is still under construction$ especially the last details of the neutron beam collimatoro There is hope that the apparatus will be ready during the coming montho

Nuclear Attenuation of High Energy Protons
An experiment is in progress to measure the nuclear attenuation of high energy protons b,y inelastic collisionso The average cross section for three energy bands 9 340 Mev to 280 Mev 9 280 Mev to 220 Mev 9 and 220 Mev to 160 Mev!P will be measured in the following elementsg Be 9 0 9 Al 9 Cu 31 Pb, and Uo At present the cross sections for C 31 Alii) Cu!P and Pb have been measured to 20 percent accuracy in the highest energy rangeo By using an 8 ino x 8 ino liquid scintillation counter with a detection efficiency of 100 percent over a circle of 7 inches diameter» it is hoped that the cross sections for Be and U can be measured alsoo It is hoped to measure all these cross sections to The effort on the modified high energy photon spectrometer which is to allow a more precise determination of the low energy region of the photon spectrometer from neutTal meson de~ay in the cyclotron target has been vi~ tually completedo This instrument will also be applied to a study of proton bremsstrahlung for proton energies below the pi 0 production threshold.,

Experiment on Charge-Independence of Nuclear Forces
For the purpose of testing charge-independence of nuclear forces~ the corrpe.rison of the production of tritons with. the production of heli~ particlesin the bombardment of deuterium b.1 high energy protons is under way.
The identification of the reaction has been definitely made and a study of its angular distribution has begun.,

On Internal Momentum Distributions of Nucleons in Light Nuclei
An extension of the work on this subject is being pursued in which a unique value for the momentum of a nucleon which scatters a high energy. proton can be determined.. The previous work did not determine unique values for a nucleon momentum in the quasi elastic scattering processes involved 9 but instead gave information about the nature of the distribution which could have given rise to the s~attered protons which we analyzed.. The instrumenta= tion involved in this extension of the experiment is in process of development.,

Fine Structure of the Synchrotron Beam
The photon beam of the Berkeley synchrotron was shown to be emitted in sharp bursts with the 47 .. 7 megacycle frequency of the electrons in the doughnut.. A two counter telescope was used to measure an accidental coinci~ dence counting rate as a function of the length of delay line in one input to the coincidence circuit.. When the length of delay line was chosen to be equal to multiples of one=half of the period of the r.,f., oscillator» the coincidence counting rate was less than about 2 counts per unit of integrated beam$ on the other hand 9 when the length of delay cable was chosen equal to multiples of the period of the rofo oscillator 9 the coincidence counting rate was of the order of 100 counts per unit of integrated beam ..
.A:n estimate of the width of a single pUlse of photons can be obtained from the measurement by unfolding the resolution function of the coincidence circuit.. If Gaussian fun~tions are assumed 9 then the r .. m .. so value of the Gaussian function that represents the time variation of the intensity of the photon beam is found to be less than lo5 x 10=9 secondso Synchrotron Studies

UCRL-1904 UNCLASSIFIED
The operation of the synchrotron during this period was reasonably satisfactoryo A certain amount of "fading" of the beam intensity during operation was observedo Some further work was done with the de Packh lenses which were installed at the last shutdowno These lenses appear to materially increase the beam at low magnetic voltages, and while not at present as effective at full beam voltage, they appear to make the beam somewhat more steady~ During the period covered by this report, the following research problems were pursued& Work was continued on the investigation of high energy photoprotons from carbon at energies of 70 and 120 Mev and at several angleso This experiment is almost completedo The time structure of the beam of the synchrotron has been studied, and under the conditions investigated (spread-out beam), definite evidence for time structure seems to have been obtainedo Preparations for an experiment to measure the production of rr+ mesons from H and D at small angles to the ~ray beam have progressed and background measurements preparatory to setting up the final experiment have been madeo The experiment on the production of nD mesons from H and D was essentially completed during this periodo It is expected that both absolute cross sections and the H to D ratio may be obtained from this experimento 7o THEORETICAL PHYSICS (~oEoCo Program Noo 5211) ' UNCLASSIFIED An investigation is being made of methods for stepwise plotting the plane orbits of charged particles moving in a static magnetic fieldo Stepwise and cumulative errors are being considered and criteria on step size obtainedo The merits of the different methods are being consideredo A short investigation has been made of the effect of chemical binding on the stopping power of materialso The equations for a charged scalar meson field interacting with a single nucleon have been examined, using an approximation method not involving an expansion in terms of the coupling constanto Rigorous solutions to these equations have been obtainede They imply that for small enough coupling constant perturbation theory is valido -9-

UCRL-1904 UNClASSIFIED
A study is being made of the radiative corrections to nuclear forces, starting from the Bethe-Salpeter equationo , Calculations of fields and various properties of the orbits have been :carried out to aid in choosing a suitable pole tip geometry for the bevatrono k study is being made of the angular distributions from inelastic proton scattering off nuclei.

Mgrk I Accelerator Program
Approximately 9S rrcent of the service manuals (over 700 pages) parts lists (over 400 pages and duplicate tracings of drawings (over 2000} have been completed and sent to Livermore o The following improvements found desirable during the initial Mark I start-up period have been designed: lo Pre-exciter line automatic node shorts with knife switch contacts and an alternative design with pneumatically operated button contactso 2o Drift tube shorting bars to permit short-circuiting the rofo b,y-pass condensers when they are not needed, thereb,y reducing the possibility of damage to the con~ denserso 3o Teflon "0" ring vacuum seals as alternates for the crane chevron packings in the cavity discharge probe and rofo voltage pick-up lineo Mechanical design studies are continuing on the application of a refractory facing for the drift tube surfaces to minimize damage caused by sparking in the 0-1 and 1-2 gapso Graphite, chromium~ and molybdenum facings have been considered, but molybdenum seems the most promising at presento · ' R 9 fa Problems The successful operation on the Mark I accelerator under vacuum conditions has demonstrated that the rofo system design is satisfactoryo It is now known that the initial rate of rise of the rofo required is approximately 2 kv/p;seo and that it should be made about five times faster than this for reliable startingo There are many ion lock levels from about 10 kv to several megavoltso The higher lock levels are also sensitive to drift tube magnetic field settings~ but fortunately at operating fields there are no bad locking problemso Experiments in the Dl and D2 oscillator positions have shown that it is possible to eliminate the big rotating loop pre-exciters by a much simpler and more convenient shift in an inductive reactance at the normal UCRlr-1904 SECRET node of the transmission lineo It is now planned to make a permanent installation of this new s.ystem in at least two positions with more to follow when additional A-2332 tubes are availableo The system planned will use these new type pre-exciters as rofo power amplifiers after the pre-excitation cycle is completedo The original planning of the 5831 type grounded grid oscillator system was done with future conversion to an A-2332 amplifier system in mind~ so that-the work involved is relatively minoro When tubes are ayailable and all the oscillators are converted~ it will be possible to eliminate reactance switching entirely and the sub-exciters as wello X-ray Monitor Vacuum Sparks and Rof 9 Decay Study has been made of the spark phenomena and rof o decay of .the Livermore acceleratoro No control of total voltage or magnetic current was exercised during this operationo Photographic results show that the configuration of the x-ray burst does not change with increasing voltage or the application of the magnetic fieldo The sparking rate and, therefore, the number of x-ray bursts increases at higher voltageo Sparking and X-rays in Mercury Pumred Vacuum S;rstems The most obvious conclusion about the 200 megacycle sparking is that it follows strictly surface gradient and is not dependent upon total voltageo From experimental work it appears that x-rays and sparking are similar pheno~ ena, differing only in that magnitude of electronic charge transporto

Ion Pump Development
The ion pump installed on the Bl cavity is now operating automatically with only routine inspectiono A cathode has been tested that gives more than two weeks continuous operationo A base pressure of 8 x lo-7 mm of mercury has been obtained under steady operation and the degree to which various sources limit this pressure has been investigatedo Currently~ experiments are being inaugurated to measure the ion density and energy distributiono An investigation is also underway to determine the practicality of a radio frequency ion pumpo Cavity Design A final drift tube table has been prepared for all but the first 30 Mev of the A-12 acceleratoro These results are final only in the sense that they contain all the information deducible from half cell studieso The resonance data necessary to complete the calculation for the first 30 Mev is being obtainedo The change from thick cylindrical drift tubes to bulbous pipes in A-12 required not only new resonance data but also new calculation of the sensitivity of A-12 resonance to dimensional deviationso Investigation of the beam acceptance in A-12 when parameters are varied has continued on the differential analyzero =11= A=12 Rofo Model UCRL-1904 SEPRET Work is A~l2 acceleratoro with silver plated plane so continuing on the rofo model of the low energy end of the The cavity will be 44 inches long and 20 inches in diameter steel wallso The drift tubes will be adjustable in three

Target and Lattice Physics Program
The work of the target and lattice physics group is centering about the following problemso lo Detailed neutron physics of the primary and sec= onda:ry targetso 2o Calculations on neutron exchange and loss in various target and lattice systemso 3o Theoretical and experimental determination of neutron flux distributiono 4o Angular distribution and production of neutrons in simulated water-cooled uranium targets with large cross sectiono 5o Energy distribution of evaporated neutrons from uranium bombarded with 190 Mev deuterons and 340 Mev protonso A major objective of the physics program is to provide a more thorough and detailed study of high energy nuclear processes in.order to place on a firmer basis the extrapolation of neutron yields to higher energies than are at present availableo Since the economics of the M~ depends critically upon the yield 9 as a function of energy 9 such a st~y may well shift attention to the 450=600 Mev range with appreciably lower cost per gram of free neutrons or per mole of producto Clover Leaf Cyclotron Development A complete report on the three phase rofo system for the 20 inch clover leaf proton cyclotron has been prepared for distributiono It covers the generation and control of three phase rofo 9 measurement of phase angle 9 phase drift in rofo amplifiers 9 characteristics of the three phase resonator 9 the theory of neutralization of dee to dee capacity 9 and a summary of experience gained from the three phase cyclotronso · Electron Model Noo III The new electron model construction has been largely completedo The tank and poles have been assembled and magnetic measurements startedo Design work on the dees is completed and construction startedo The electronics installation should be ready and tested by the time it is neededo Preliminary results indicate that the magnetic field before shimming is within one percent of the· theoretical value desiredo · An apparatus is being developed to look for short-lived alpha emitters by means of photographi~ plates mounted in the cyclotron near the targeto The plates are shielded b,y a shutter which is opened a fraction·of a second after the beam is shut off., Alpha particles emitted b,y activities in the target will strike the plates~ and their energies will be determined by the positions as well as lengths of the trackso Alpha Spectrum of Gm 2 42 A. third alpha group has been observed in the decay of cm242 by means of the magnetic alpha spectrograph., This group is highly hindered; ioeo, its decay rate is lower than corresponds to its decay energyo This decay goes to a state of Pu_238 about 146 kev above the ground stateo This group was previously assigned tQ_crnf43~ but a new sample of curium» produced by neutron irradiation of Anf4! at Chalk River and containing a different ratio of curium isotopes» allowed the assignment to be made definitely to cm242.

Beta and Gamma Spectroscopy
The v':2rr magnetic beta spectrograph is being fitted with a crystal scintillation counter adjacent to the source and with pulse analysis and coincidence circuits to allow coincidence measurements between electrons and photons of known energiese Another project which is planned is a double thin lens beta spectrometer to allow coincidence measurements between pairs of electrons of known energyo Crystal Structure of TlClJ An x-ray powder pattern of T1Cl3 shows it ·Go be isostructural with YCl3 9 several rare earth trichlorides, and A1Cl 3~ with lattice dimensions slightly less than those of LuCl3o Properties of cnf-38 cm238 was produced by the (a 9 5n) reaction on Puf39 and was found to decay with 2o3 hro half-lifeo The alpha particles, have energy 6o52 Mevo The electron capture. to alpha decay ratio is 240 ± 50o The assignment is based on the presence of ~34 as a decay product and coincidences of pairs of alpha tracks of the correct energy in a photographic emulsion in which the activity had been depositedo The two alphas are from the successive decay of cm238 and p~34o During the past month syntheses have been completed on the following carbon-14 labeled compounds: sodium acetate-l-C14, isobutyl-l-cl4 bromide, ethanol-l-c14 1 and 2 ,3-dime~l-2,J-dihydroJcybutane-l-C14 (pinacol).. Syntheses are underway on glycine-2-cl4, leucine-3-Cl4, and aspartic-4-cl4 acido ~e labeled pinacol is being used to determine the isotope effect involved in the pinacol rearrangemento.
-14- UCRL-1904 UNCIASSIFIED The actinometry of a cobalt-60 gamma-radiation source is underway .. This source will be used to determine the effect of gamma radiation on various substances of importance in animal biochemistry ..
The excretion pattern of morphine from a normal person (as distinct from a cancer patient) is being determined.. An 0 .. 9 p.curie dose of morphine-N-methyl-cl4 has been administered and the rate of appearance of radioactivity in the breath, urine, and feces is being established ..
Further work in biochemistry includes (1) studies of the rate of metabolic oxidation to C02 of carbon-14 labeled fatty acids in normal and hypophysectomized rats and of the effect of the simultaneous administration of various drugs on that rate, (2) isolation of cholesterol from various blood serum fractions for determinations of the amounts of the companion sterol, A7-cholestenol ( 11 lathosterol"), which are present, and (3) preparation of a large amount of ~7-cholestenol which will be used in an animal feeding program designed to shed some light on the possible importance of this compound in the appearance of atherosclerosis ..
The continuing plant biochemistr,y research has focused its attention during the past month on (1) the effect of antibiotics on the pattern of appearance of labeled compounds after exposing green algae to radioactive carbon dioxide, (2) degradation studies designed to determine the amount of and rate of appearance of carbon-14 in the various positions of the sedoheptulose obtained from the algae, (3) kinetic studies of a more detailed nature concerning the rates of appearance and disappearance of various metabolites of importance in photosynthesis, and (4) determination of the relative amounts of carbon-14 in the labeled purine and p,yrimidine bases obtained from the nucleic acids of photosynthesizing algaeo · The possible toxic effects resulting from a large number of roentgenequivalent-physical which were delivered to rat plasma from the cyclotron are being studied, using I 13Ltagged thyroglobulin as a toolo Studies of a comparison of the relative effects of alpha and beta emitters have been initiated in rats, using Na24 and A t211 ...

Radioautography
Work has been completed upon the autopsy material from the fission product animals, rats and monkeyso Plans are under way for autopsy studies of the astatine-injected monkeyo =15-Radiation ChemisttY UCRL-1904 J1NCIASSifiED Work has continued on the separation and identification of products of the irradiation of acetic acid and formic acid under various conditionso Additional information has been obtained on the identity of certain of these productso Present work is directed toward quantitative determination of radiation yield valueso

MEDICAL PHYSICS
Part B (AoEoCo Program Noo 6400) Effects of Altitud.e on the Life Span of the Red Blood Cell UNQIASSIFIED The changes induced in the blood volume of rats b,y simulated high altitude conditions have been studiedo These changes were measured by infusing Fe59 labeled red cells from a donor rato At 15 1 000 feet an unexpectedly rapid equilibrium red cell volume was reachedo After 8 days at this altitude the blood volume was approximately twice the normalo To achieve thi~9 red cells were produced at 6 times the normal rateo Exposure of animals to other altitudes has shown that for mechanical reasons it is unlikely that the necessary hemoglobin increase would be achieved at altitudes much above 20 9 000 feeto Biological Effects of Radiation on Micro-organism § Haploid» diploid, triploid and tetraploid yeasts have been developed in a single yeast straino Irradiation with x=rays definitely shows that the triploid and tetraploid are more radiosensitive than are the diploido Also sporulation of the tetraploid strain into lesser chromosome numbers accompanied a relative decrease in radiosensitivityo This is in contrast to previous reportso This study will be presented in detail in the next Quarterly Progress Reporto Nupleic Acid Studies An epidemic in the mouse colony has been controlled, and we have been able to continue mouse irradiation survival studieso The mouse infection, epierythrozoan coccoides, particularly interferred with the nucleic acid turnover studies as it was associated with splenic enlargement and in~ creased desoxypentose nucleic acid turnover of spleen and livero Although the infected mice had greater nucleic and formation rates, in the unirradiated state they did not exhibit an increased resistance to irradiation as do animals whose desoxypentose nucleic acid turnover is increased b.1 appli~ cation of embryo extractso Current studies are on the mechanism of the radiation protection induced by tissue extracts after irradiationo Lipoprotein Studies

TJCRL-1904 UNClASSIFIED
The effect of radiation on lipoprotein metabolism continues along the line of studying the alteration of the stepwise conversion of lipoproteins induced b.r irradiationo llo HEA.LTH CHEMISTRY (AoEoCo Program Noo 5311)

UNQIASSIFTED
The Equipment Development group has continued work on the following major projects for the chemistry department, plus numerous smaller items: lo Preparation for the receival of a highly active Canadian pile-bombarded sample, the equipment for which was partially described in the monthly progress report for the period ending January 15, 1952, is essentially finished and the sample will be opened in a week or soo 2o Equipment for the second phase of processing the americium milked from plutonium slug-type cows received from Los Alamos was completed and is awaiting use by the chemists a 3o Equipment for recovering americium from barrels of sol~ tion from Hanford is reaching completiono 4o Equipment for recovering neptunium from materials received from Hanford is completedo 5o Eleven gloved boxes were readied by the Berkeley Box groupo 6o Room 107 ( 11 Cave RoOin' 1 ) , Bldgo 5, whose contamination was described in the last monthly progress report, was repainted and refloored after decontamination and has been put back into useo l2o PlANT AND EQUIPMENT Winding has been completed, and tests are scheduled to begin July 23rdo The ion gun is being reworked and there is no progress reported on the pole tips and pole bases due to the steel strikeo Radiological Laboratory at the UoCo Medical Centero (Program Noo 9600o 6-424-9008) Plans for the acoustical treatment of the accelerator room have been completed but no bid has as yet been acceptedo PROGRAM .