THIS DOCUMENT CONSISTS OF r NO l OF 4 7 PAGF S COPIF S SERIF a 13 May-1945 · TCh Major General L R Groves From R C Toiman Subject Report on First Trinity Teet l Purpose of Test This memorandum gives a brief description of results obtained in the i'irst Trinity Test carried out on 7 May- 1 945 The purpose or this test was to obtain preliminary information i'rom the deton tiqn ot 100 tons of ordinary high explosive as to the success to be expected from observational methods and from administrative procedure• proposed for the final test with nuclear explosive The section headings 1n this memorandum agree with those in 127 memorandum of 17 April 1945 on the Program for Trinit7 Teat• to whi cb reference may be made for a clearer understanding or th• purpose of the whole program The present memorandum is written at a tiae when the data provided by the first test have for the most part not been worked out but when it is possible to give an overall picture of the character of the test and to state which measurements appear to have failed or succeeded 2 • General Character of the Test The test was carried out with 100 tons of high explosiv stacked on the platform of a twenty foot tower as described in more detail in the previous memorandum The stack o f high explosive was provided With tubes containing radioactive solution to sillulate at a low le'ftl of aotiVity the radioactive products expected from the nuclear 8 Xplos1on Keasureaents of blast effect earth ehock and damage to apparatua and to apparatus shelters were made in general at •eoaled-in diets noes as compared with the distance• proposed tor the final •hot lleasui-ements to determine cross-talk between circuits and photographic observations were in general carried out at the f ull di stances Proposed f or the final shot Th8 advanced from the original dat e scheduling o f the test was troduction ot apparatu• On the 5 Ila basiT to 7 Ma7 to al low for fur ther in the tilae seleoted t or the •hot lfa • of continuing weather f orecas t1ng f f nth a de1ay of only 8 A M and it was aotual 17 pull pt properl7 ranged for 37 - 00 1utes to allow the o bservation p1ane dropping its air-bome instrumeDW• 'hlrft 1 111L11drr - -- Ulllld t r i Ae U U Ill I I • tW W II 111111 - • • Ct _ flQ -la DECLASSIFIED Authority N tJ 2 2 30 D · A r Memo to General Groves - 2 - 13Mayl945 The detonation was evidentJ y high order It led to the production of a highly luminous sphere which then spread out into an oval form This we a followed by the ascent of the expected hot column which mushroomed out at a height of some 15 000 feet at a level where atmospheric instability was indicated by meteorological observation and then drifted eastward over the mountains The illumination and sound were detected at the Almogordo Air Base 6o miles away by an observer who had been prewarned Earth shock was imperceptible at 10 000 yards and at the base camp 10 miles away The explosion seems to have aroused little comment in neighboring tolms 3 Program of Measurement and Observation As described in more detail in the previous memorandum the primary measurements and observations to be ta ken in the final test may be grouped under the following four headings 1 Behaviour of the Implosion 2 Nuclear Energy Released 3 Damage Effects Produced 4 Overall Behaviour of the Explosion and its After Effects In this preliminary test which involved neither an implosion notnuclear explosive only subsidiary experiments could be carried out in connection with the first two headings In addition to the program of primary measurements and observations there were also programs of measurement in connection with meteoro' logical observations and health control 4 Organization for Carrying Out the Program The organization for carrying out the program was substantially as described in the revious memorandum Including military per Jonnel 1 t inVolv d total pf ximately 200 men In view of the circum- stances a o appro ied out on a very tight time schedule and 1 to' at the test was carialr run the organization functioned 8 be regarded as a tr ' wi th considerable success affected by delays in procurement The tightness of the schedule was 0 me apparatue arrived only at d transport a tion This meant thaf night work for many persons e last moment and involved fever 8 f the actual test It is hoped oton one or more nights preceding tba t O 8 more realistic scheduling cure this in the final test a by • aw c t ' sf llt Un tld S wiltln ' - manHW 'Act J 1 C 5i1J 31 • 3Z 'Is I Ir 1rr 11'1111 ti let C - In lff' It II •• '' 'bf• I DECLASSIFIED - - j Authority J tJ D 7 3oD-39 I Memo to General Groves - 3 - 1 3 May 1945 allowing for time delays in procurement b by the provision of additional transportation part of which will be assigned to individual groups who will then be responsible for its upkeep c by' improvements in key roads which will reduce transportation breakdown and d by the setting of a definite date sufficiently in advance of the test beyond which further apparatus cannot be introduced into the experimental area In connection with scheduling it should be remarked that the tightness of the time schedule for this preliminary test has the advantages of emphasizing the need for a less hurried procedure in the final test and of providing a longer interval of time to prepare for the final test There was some criticism in connection with arrangements for intercommunication and timing Radio-communication was often weak and subject to interference It is planned to cure this by installing more telephone communication by obtaining better radio sete end if possible by obtaining more than a single radio frequency for use The arrangements for sending time signals to various apparatus stations actually worked well but involved a large amount of last minute work by an emergency group It is possible that a separate group TR-7 will be set up to take charge of radio telephone and timing problems ' The organization is a temporary one set up specially f or the Trinity Tests and involves the placing of heavy responsibilities on younger men including SED boys This means a certain looseness in the organization and inexperience on the part of some of the operators In spite of this the organization functioned as well as could be expected and has no'ff been through a good shakedoffll PNp ratory to the final test e following individual failures of personnel came to my attentio Tiro operators probably sED boys failed to push buttons at the north n and south 10 000 yard stations to actuate cameras This will be cured by putting these cameras on automatic controls One operator failed to close a switch for the blast operated flash bombs Two operators became unduly alarmed when their jeep broke down in the middle of the night and spent 80 much time in ineffectual attempts to make repairs that they failed to put water into an impulse gauge This should be cured by better transportation and ro ds Ce tain responsible persons ent into the area without authorization to distribute mice for biological eXperiments with consequent damage to electrical connections w f but more detailed description of the diff e may now turn to a dbribe e - tions that were made using the same erent measurements an o s •u headings as in the previous memor andum lhl 1 1111111 c llllllfflS informa119fl Jfflctlfll · of 1M 'flil •---11111111'1 St1111 wiltnll he eaJll - - of a e Unitld JI IN 32 11 1rtn • c - -n let U S C 5111 • fllllllll If --- • lhe _ I I ill - ' tn - t II F alllll1d - - l DECLASSIFIED D3 I Authority N tJ 2 30 Memo to General Groves 5 - 4 - 13 May 1945 Behaviour of the Implosion • · Detonator Simultaneity No measurements of detonator simultaneity were made in this test which did not involve thirty-two detonation points as in the final bomb Such measurements are standard at Los Alamos and Kingman b Time Interval between Detonator and Nuclear Action No measurements of time between detonator and nuclear action were possible • £• Determination ofd for the Nuclear Reaction The cable and recording apparatus to be used by Wilson in the measurement of were tested for cross talk The accidental signal level was a few millivolts so that the final apparatus ill be designed to give its tru signal at a level of a bout one volt 6 Nuclear Energy Released • Delayed Neutrons The equipment of Williams for measuring delayed neutrons was installed at a scaled-in distW1ce and suffered no damage • Q• Delal _Qa 'IUlla Rays The apparatus of Moon for measuring delayed gamma rays was in8talled and gave r ecords Tests were made on equipment for Segr6 1 s method which withstood air blast and earth shock • £· -22 ve ·sion of 49_to Fission Prq_duct 'fhe Hanford slug was successfully dissolved and introduced into the 1Jile which then had a beta ray activity of 1000 curies and a gamma r y activity of 400 curies _On the basis of simple scaling-up of the RaLa shots it • ould be calculated that 10% of this activity would remain in the · soil within a JOO foot radius after the shot Actually only 2% was found in that radius indicating as might be expected that simple scaling laws do not prop rly allow for the increase in updraft with increased charge A distriootion formula for the activity as a function of distance was determined It was also determined that the local distribution in the soil was su ch as to permit alpha particle counts without difficult chemical separation The rocket method for obtainln soil samples from the crater was tested and found satisfactory uand the use of shielded tanks in connection With the final sam ling was also tested 7• Dams J e _g t_ ects Produced • • Blast Pressure at Ground Level_from__fiezo Gauges Eleven quartz blast gauges we e installed and nine records obtained These have not yet been analyzed in detail Some of them show cross talk but a certain amount of reliable data will cer inly be obtained llill dltu12m11 Clllllllna itllitnnatio11 affecti I tht _ of the Ullilld Ila wifiin 1he ring o_ Act U I C 50131 _ 32 1rar11111• • llterMlalien If 111 C in_ a -•pu llbd _ no Memo to General Groves co - 5 - 1 3 May 1945 - r b £Last Pressure at Ground Level from Condenser Gauges Eight inn nser gauges were planned for use but only one actually was s lied and 1 t gave no record In view of the success of a siaiilar airborne gauge so me success in the final test is to be expected • £· Blast Pressure at Ground Level from Excess Velocity Six receivers were installed to pick up the blast wave and record its time of arrival These worked well on the small calibration shot but gave evidence of much cross talk hash on the main shot It is not yet known whether the records can be satisfactorily analyzed Improvement might be introduced by lowered sensitivity for the main fhot 86 compared with that needed for the calibration ahot and by eading the signals into separated rather than a single ampli£ier Forty-seven flash bombs to be operated b7 arrival of the blast were installed Photographic observation was then to be used to determine blast pressure from excess velocity Only two flash bombs went off due to personnel failure to close a switch box g Peak _Pressure at Ground Level from Paper Gauges Twenty-nine int gauges each with twelve boles covered with aluminum foil were roduced to measure peak pressures at dif£erent distances and f unctioned SUocessf'ully Fiveei n Impulse at Ground Level from Piston•Acting on Fluid f t 0 strtunents of Los Alamos design were planned and one satis ac rUy in stalled for · measuring blast 1m·pu1 88 b f 0 llOn a ug - - the acti A on of a piston forcing water through a set of constrictions be good record was obtained but without timing marks it can probabl y uee a J Yzed as a consequence of the constancy of speed of the motor did to drive the recording disk One instrument of British design bear t operate entirely aatisfa torily perhaps from sand in the pa gs since it showed a velocity which increased during the ssage of the blast wave in co d Pressure at Higher Levels from Condenser Gauges Three t enser gauges for measuring blast pressure were dropped over the Pl get from a height above ground of 15000 feet by the observation frane One radio receiver in the plane was known to be out of order ex 1 0 fire and one recording instrument failed The other gave an in an 1 t Pressure time record The three parachutes had to be dropped rel instead of successively as planned owing to f ailur e in bomb ease mechanism The plane used was a B-29 assigned to the project ff rdJ at a any shock was felt by the plane when the blast wave reached it istance of about four miles • f ' _ st 9 e tlallM Sllll8wilhll lhe • Uflffll of ltrt 32 1- ra111111iNi• t its n - 11111• I v s c u 31 • a iOfta • At Jr the rftNllion I _ ___ _ __ D E C L - 1Authority NtJ 'D7 3i D L Memo to General Groves - 6 - 13 May 1945 _g Earth Shock · Six converted geophones were used for mea suring velocities of earth motion and gave satisfactory records which have not yet been analyzed Survey is now beine made to determine the permanent displacement of stakes driven into the ground around the point of explosion The crater was about 5 feet deep and 30 feet in diameter which was smaller than expected This may be partly due to the effect of the heavy concrete footing for the tower 8 Overall Behaviour of the Explo ion and its After Effects a Size1- Shape BebRviour ¥d Path of the Ball of 'ire Three out of three Fasta x cameras 1000 frames per second at 800 yards and t out of two at 10 000 yards operated satisfactorily Two Mitchell cameras at 10 000 yards operated satisfactorily one for 30 seconds and the other for the full 1000 seconds planned u t for development Films have R· tl _on and Tempe ture of Ball of Fire Two out of two 1lll4-r npect rographs were in operation there was some uncertainty about the focussing of one of these The films are being developed The Bausch Lomb spectrogrsph and the movie camera with filters were on low priority for this test Wld were not installed The drum camera with photo cells gave no record because of cross-talk The thermocouples and galvanometers appeared to function satisfactorily £· haviour of Hot Column Three Fairchild Aero Cameras were installed The two at 10 000 yards north and south did not operate because of personnel failing to push the necessary buttons The one at 35 000 yards continued to take pictures until 9 00 A M -5 Mach Wave and Air Velocit_y The proposed photographs of a suspended primacord were not obtained owing to failure to get the balloons up from which it was to be suspended due to poor quality balloons which burst and low helium supply Photographs of a horizontal stretch of primer cord appear to have been obtained The primacord detonation was dimmed rather than brightened by the blast 9 MeteQ _rological Observations Meteorological observations are being continuously undertaken to obtain a good idea of behaviour in the particular location They would be greatly assisted by the proposed installation of a teletype weather service which has still not come through - r I DECLASSIFIED - - D-3 j Authority NtJ Y7 30 - a Memo to Gen erQ L Groves 13 May 1945 - 7 In con serv1 nection with th8 th ce was proVid d · -present test excellent meteorological at 7 May would fe • On 23 Apr il it was successfully forecast forecast was mad all in a good weather period -On J May successful and Vi sibilit as to the surface wind direction upper air flow forecasts w Y be expected at 4 00 A M on 7 May Similar 4 00 AM 8 8 made on 5 May and at 5 00 P M 6 May which gave • • an also 9 to l0 30 A M as operationally possible to Temperature humidity and wind velocities at all levels up r d30 000 feet were measured with the help of radio-sondes and a art at 1 30 A M 3 00 A M and 4 '51 A M on 7 May before and j us after the explosion ·· P E Church arrived in time for the test and was helpfui in discussing meteorological methods and problems 10 Health Control Radioactive monitoring was carried out by Hempelmann during the processes of slug solution and introduction into the pile Monitoring after the explosion in the neighborhood was carried out by Hempelmann and checked by Anderson The level of activity in the final crater was low enough to be safe for several hours exposure The dissolving unit is to be covered with fresh earth and surrounded by a guard fence 11 Conclusion The test appears to me to have been successful as a trial run In the final test it is to be hoped th at a larger proportion of tbe measurements will be successful but even if this were not the case sufficient data would be provided to answer a considerable proportion of the necessary questions There is common agreement among those concerned as to the steps suggested which should be taken to insure greater success in the final test Among these suggestions one of the most important is that of setting an advance date beyond which further apparatus especially electrical apparatus cannot be introduced into the experimental area This will allow time for plenty of dry runs and elimination of cross-talk Improvement in transportation equipment and key roads should be sought Special attention should be given to the early procurement and testing of those very important kinds of apparatus that could not be tried in the present partial test Richard C Tolman Vice-Chairman NDRC Copies #1 - General Groves #2 - Files #3 - J R Oppenheimer #4 - K T Bainbridge fM CNlliDa illfw1lla1iln in '' ' · ___ af _ United Slllllwlt III lilt 01 lu E pi - _IJ I O 9'lt 31 11111 • • - L - - - - - - - ' -· _ Ill- 1 _ _ _ r- D E - C L -A- -S S -IF-IE_D_ CN11111111- -• • QmDrT Authority N tJ SY7 30 D'