.' LYON-RK 278 71-0030 NOTES which is exact at all times except at the peaks ancltroughs of the data. 4 Equation (6) should be particu larly usefu l in the vicinity of shocks, acceleration \\'a\'es, and other rapidl~ ' changing accelerations where Taylor's series expansions are th e least valid. In a ll other regions, the ~T centering of th e velocity interferom eter equation mentioned in Ref . 2 is extremel:' good; i. e., errors resulting from its usc arc small compared to other errors in th e system, such as risetimes of photomultiplier tubes, determining F(t ), etc. i- • This work was supported by the United States Atomic Energy Commission. 1 L . M. Barker, Bclta!'ior oj Delise Media UI/der [Jigh DYllalllic Pressures (Gordon and Breach, New York, 1968), p. 483. 2 L. M. Barker and R. E. Hollcnuach, J. App!. 1'11)'s. 41, 4208 (1 970). 3 R. J. Clifton, J. App\. Phys. 41 , 5335 (1970). • By employing t\\'o photomult iplier tubes arranged to record data which is 90° out of phase, the indeterminacy at peaks and troughs ca n be avoided . I. Double-cham l powder conlni lllf. FIG. ; .It! nl' :11 I Double-Chamber Powder Contain er for Flame Fusion Crystal Growth JOHN L. SAMPSON Air Force Cambridge Research Laboratories (AFSC), L . G. 1IaJ/seom Field, BedJord, },fassachusclfs 01730 (Received 28 September 1970; and in final form, 19 October 1970) A DOUBLE-CHAMBERED powder container has been developed for use in flame fusion crystal growth . It permits rapid in terch ange of chambers and replenishment of powder without di turbing the flame on the growing crystal and may be used to change the composition of the crystal 0)' to replenish the supply of powd er for extended growth. The mechanism consists of an inner assembly, an outer hopper, and an outer coyer. The inn er assembly includes the double-chambered cylindrical container a (Fig . 1) pivoted to bracket b about a horizontal axis. The container is 9 em outer diameter a nd 8 em long. Th e bracket is attached to inner cover c, which is sealed with an O-ring d against the outer cover e. The chamber is sealed with an O-ring f against outer hopper g when in either vertical orientation . The lO\\'er end of the outer hopper is conical, \yith its inn er surface tangential to the circle through which O: ring f moves as the container rotates. O-rings d and f provide isolation for the inn er assembly, permitting it to be shaken by th e impact of hammer h. The outer hopper has an inner diameter of 12 cm. O\'er-all dimensions of the device arc 18 cm diameterX 27 cm high. A large torque would be required to turn the con tainer while th e lower O-ring is eated. Adjusting screws i are, therefore, prO\'ided to loosen this seal before rotation and 10 burner retighten it afterwards. Bar magnets j, fastened to tlte container \vall in a parallel configuration, are acted UpOIl by a permanent magnet exterrial to the outer hopper II rotate the container. Each end of the container is closed with a fine 1l1 ('~h screen k held in place by a spring clip 1. Powder from thl lower chamber is shaken through the screen by the aclillil of the hammer and carried through th e bottom of tIll outer hopper to a burner by oxygen introduced throll)!!' port m. R eplen ishment of the powder is accomplished by seatin. the lower O-ring t ightly, opening \Villdow n, and removin:: the upper spring clip and screen. After replacing th . screen, clip, and window, the lower O-ring may be looscnl:d and the container rotated. Novel Sample Container for Reaction Rat'; Studies at High Pressure RICHARD K. LYON Corpora.le Research Laboratories, Esso Rcsea rch alld El1gillcering Company, Linden, Ntr'.L' J ersey 07036 (Received 11 Sep tember 1970; and in final form, 21 October 11);11 T has.been a conUllon pract ice in study.ing re~cti'on r.al l ' at 111gh pressure to place the reactlOn nuxture III .1 sample container capable 'of transmitting an extern.d hydrauli c pressure. I The author wished to study the elTl'rt of pressure on a catalyzed reaction, using a catalyst who,< I It I I.tt , ! HOIlkl :;::"l t IlI id~ 1o'Il1pl .. Il l ' I tu bi ll ,. OTE S li,·ity was not readily reproducible. This required the dclt preparation of identical samples uncontaminat ed \ con tact with anything except glas , TeHon, and dry rrugen . None of the literature designs were suitable so IWW sample container was developed. This new sample "olainer may be of more general interest since it permits !Il' reaction temperature to be more accurately controlled 'leI permits the reaction to be run for short but precisely :, Ii neel reaction times. Il:!tches of samples are prepared by forcing the reaction ouble-chaml. lixture into a length of 0.13 cm 0.c1.XO.07 cm i.d. Teflon cr container. .hing (22 gauge) with sleeves of annealed stainless steel ' ulling (0.21 cm 0.d.XO.16 cm i.d.) distributed along it. rhe first portion of the reaction mixture going through '111: tubing serves as purge. The steel sleeves are then pi nched shut and the Teflon tube is cut into segments, 1110 sleeves per segment. The steel tubing sleeves are quite It isfa ctory as one-close-one-open valves. Provided that the sample containers are completely full of liquid, they survive compression to 7X103 kg/ Cll12 \VitIl r Ire faiJures. The bursting strength of the containers is Inough to permit filling them with such high vapor pressure liquids as normal butane. stened to th I t has been a common practice in high pressure reaction re acted upo~ r.l te studies to place the high pressure vessel in a conIter hopper t 'rolled temperature bath and assume that the temperatllre of the reaction mixture inside the sample container h a fine me, :n ide the high pressure vessel is the same as the bath \"der from til t~ ll1perature . With these small diameter sample containers . by the actio one may use 1.27 cm o.d. XO.32 cm i.d. high pressure DoUom of th'tu bing as the high pressure vessC'!. The use of a narrow :l.uced thrOUgtlf<:ssure vessel provides tight thermal coupling between he reacting mi,ture and the ' bath, and minimizes the :hed by seatin Irlllperature difference between the reaction mixture and and removin the bath which may arise owing to both exothermic ~ replacing th ~acti.on an~ ~h~ nearly adiabatic compression the sample lay be loosenr ']lenences Imtlally. :\ narrow pressure vessel permits short reaction times () be well defined. It has been common practice to load he sample container into a cold pressure vessel and to ppl)' pressure before heating to the desired reaction R t t mperature. This procedure has the advantage that reaction a rtion can occur only after the reactants a re at tbe desired re rcssure. However, the reaction time is well defined only it is long compared to the tim e necessary to heat the wrcll and re sure vessel. L et us define the effect ive heating time ey 07036 ' the time for 95% of the temperature change to occur, 21 October 19i e., three times the over-all thermal relaxation time lIllstant TI. The time constant for relaxation of temperaIg reaction rail re differences between the center and surface of the n mixture in \ lindrical pressure vessel is 72=r2/a where rand (l' are ng an extern'le pressure vessel's radius and thermal diffusitivity, study the cllc1.,pectively. For perfect heat transfer between the vessel catalyst who. rface and the bath, 71 = 7 2· Howe\,er, it is desirable that I 279 71~ 272, in order to minimize th ermal stress. The th ermal stress of heating is additive to the stress owing to internal pressure. 2 Hence, a heating time of 6r~/a is possible, which for a 1.27 Clll o.d. steel pressure vessel is 24 sec. In the author's experiments, heating times of 1 min were short enough and were easily achieved. I The designs given in the literatu rc are revicwed by K. E. \Veale, Che1l1ical R eaction otlIigll Pressllres (E. & F. N. Sron, London, 1967), p.95. ~ For further di scussion see Ref. 1, p. 86. Irradiation Damage by Beta Particles R. R. COI.TMAN, J R. AND C. E. KLABtlN"DE Solid .State DiI'isiolt, Oak Ridge National Laboratory* Oak Ridge, Tennessee 37830 AND W. J. . WEBER Wiscollsin Slate Ulliversity, Oshkosh, Wisconsill 5--1901 (Recei"cd 8 September 1970) THE radiations emitted fro J? certain radioactive clements a.re conlllonly used to produce different types of irradiation damage in materials. Alpha particles emitted from radioactive polonium and gamma. rays emitted from radioactive cobalt arc two examples. The results of the experiment reported here demonst rate tha.t fast electron damage can be produced in a metal by beta. particles emitted from a radioaclh"e source. A survey of the nuclear properties of easily obtainable clements, which could be fabricated i~to the proper shape, showed that gold having a 98.0 b cross section and a 64.8 h half-life provided the highest specific activity that could be achieved in a reasonable time. The maximum energy of a beta particle emitted by gold is 0.95 ?ieV . (The cross section for defect production by the accompanying 0.41 MeV gamma ray is negligible compared to the cross section for defect production by the beta particle. I) Gold foil 0.025 mm thick rolled into a cylinder 3.81 crn lon g with an inside diameter of 0.25 mm served as an emitter. An aluminum wire specimen 0.13 mill diameter was anodized for in sulation and inserted into the gold cylinder. Curren t and potential leads were soldered to both gold and a.luminum for the measurement of the residual resistance changes expected in each. This assembly, mounted on a fired Lavite holder, was irradiated in the ORXL bulk shielding reactor for 113 h at about 45°C to an integrated thermal neutron dose of 5.3XIOls n/ cm 2• Twenty-four homs after irradiation (to allow some decay of the associated radioactive copper leads) the assembly was lowered in to a shicldedliquid helium vessel where in - !