Austrian-born British nuclear physicist
Otto Robert Frisch
OBE
FRS
[1]
(1 October 1904 ? 22 September 1979) was an Austrian-born British
physicist
who worked on
nuclear physics
. With
Otto Stern
and
Immanuel Estermann
he first measured the
magnetic moment
of the
proton
. With
Lise Meitner
he advanced the first theoretical explanation of
nuclear fission
(coining the term) and first experimentally detected the fission by-products. Later, with his collaborator
Rudolf Peierls
[1]
he designed the first theoretical mechanism for the detonation of an
atomic bomb
in 1940.
[2]
Early life
[
edit
]
Frisch was born in
Vienna
in 1904 to a
Jewish
family, the son of Justinian Frisch, a painter, and Auguste Meitner Frisch, a concert pianist.
[3]
He himself was talented at both but also shared his aunt
Lise Meitner
's love of physics and commenced a period of study at the
University of Vienna
, graduating in 1926 with some work on the effect of the newly discovered
electron
on salts.
Nuclear physics
[
edit
]
After some years working in relatively obscure laboratories in Germany, Frisch obtained a position in
Hamburg
under the
Nobel Prize
-winning scientist
Otto Stern
. Here he produced work on the diffraction of atoms (using crystal surfaces) and also proved that the
magnetic moment
of the
proton
was much larger than had been previously supposed.
[4]
The accession of
Adolf Hitler
to the chancellorship of Germany in 1933 caused Otto Robert Frisch to make the decision to move to
London
, where he joined the staff at
Birkbeck College
[5]
and worked with the physicist
Patrick Maynard Stuart Blackett
on
cloud chamber
technology and artificial
radioactivity
. He followed this with a five-year stint in
Copenhagen
with
Niels Bohr
where he increasingly specialised in
nuclear physics
, particularly in neutron physics.
Nuclear fission
[
edit
]
During the Christmas holiday in 1938, he visited his aunt
Lise Meitner
in
Kungalv
. While there she received the news that
Otto Hahn
and
Fritz Strassmann
in
Berlin
had discovered that the collision of a
neutron
with a
uranium
nucleus produced the element
barium
as one of its byproducts. Hahn, in a letter to Meitner, called this new reaction a "bursting" of the uranium nucleus. Frisch and Meitner hypothesized that the uranium nucleus had split in two, explained the process, and estimated the energy released, and Frisch coined the term
fission
, adopted from a
process
in biology, to describe it.
[6]
[7]
Political restraints of the Nazi era forced the teams of Hahn and Strassmann and that of Frisch and Meitner (both of whom were Jewish) to publish separately. Hahn's paper described the experiment and the finding of the barium byproduct.
[8]
Meitner's and Frisch's paper explained the physics behind the phenomenon.
[9]
Frisch went back to Copenhagen, where he was quickly able to isolate the pieces produced by fission reactions.
[10]
As Frisch himself later recalled, a fundamental idea of the direct experimental proof of the nuclear fission was suggested to him by
George Placzek
.
[11]
[12]
Many feel that Meitner and Frisch deserved Nobel Prize recognition for their contributions to understanding fission.
[13]
In mid-1939 Frisch left Denmark for what he anticipated would be a short trip to
Birmingham
, but the outbreak of
World War II
precluded his return. With war on his mind, he and the physicist
Rudolf Peierls
produced the
Frisch?Peierls memorandum
at the
University of Birmingham
, which was the first document to set out a process by which an atomic explosion could be generated. Their process would use separated uranium-235, which would require a fairly small
critical mass
and could be made to achieve criticality using conventional explosives to create an immensely powerful detonation. The memorandum went on to predict the effects of such an explosion?from the initial blast to the resulting
fallout
. This memorandum was the basis of British work on building an atomic device (the
Tube Alloys
project) and also that of the
Manhattan Project
on which Frisch worked as
part of the British delegation
. Frisch and
Rudolf Peierls
worked together in the Physics Department at the
University of Birmingham
1939?40.
[14]
He went to America in 1943 having been hurriedly made a
British citizen
.
Manhattan Project
[
edit
]
In 1944 at
Los Alamos
, one of Frisch's tasks as the leader of the Critical Assemblies group was to accurately determine the exact amount of
enriched uranium
which would be required to create the critical mass, the mass of uranium which would sustain a nuclear chain reaction.
[15]
He did this by stacking several dozen 3 cm bars of enriched uranium hydride at a time and measuring rising neutron activity as the critical mass was approached. The
hydrogen
in the metal bars increased the time that the reaction required to accelerate. One day Frisch almost caused a runaway reaction by leaning over the stack, which he termed the "
Lady Godiva assembly
".
[16]
His body reflected neutrons back into the stack. Out of the corner of his eye he saw that the red lamps that flickered intermittently when neutrons were being emitted, were 'glowing continuously'.
[16]
Realizing what was happening, Frisch quickly scattered the bars with his hand. Later he calculated that the radiation dose was "quite harmless" but that if he "had hesitated for another two seconds before removing the material ... the dose would have been fatal".
[16]
"In two seconds he received, by the generous standards of the time, a full day's permissible dose of neutron radiation."
[17]
In this way his experiments determined the exact masses of uranium required to fire the
Little Boy
bomb over
Hiroshima
.
He also designed the "dragon's tail" or "guillotine" experiment in which a uranium slug was dropped through a hole in larger fixed mass of uranium, reaching just above critical mass (0.1%) for a fraction of a second.
[18]
At the meeting to approve the experiment,
Richard Feynman
, commenting on the transient danger involved, said it was "just like tickling the tail of a sleeping dragon." In the period of about 3 milliseconds, the temperature rose at a rate of 2000 °C per sec and over 10
15
excess neutrons were emitted.
[19]
Return to England
[
edit
]
In 1946 he returned to England to take up the post of head of the nuclear physics division of the
Atomic Energy Research Establishment
at Harwell, though he also spent much of the next thirty years teaching at
Cambridge
where he was Jacksonian Professor of Natural Philosophy
[5]
and a fellow of
Trinity College
.
Before he retired he designed
[20]
a device,
SWEEPNIK
, that used a laser and computer to measure tracks in
bubble chambers
. Seeing that this had wider applications, he helped found a company, Laser-Scan Limited, now known as Laser-Scan Engineering Ltd., to exploit the idea.
Retirement
[
edit
]
He retired from the chair in 1972 as required by University regulations.
[20]
He died on 22 September 1979.
[5]
References
[
edit
]
- ^
a
b
c
Peierls, R.
(1981).
"Otto Robert Frisch. 1 October 1904 ? 22 September 1979"
.
Biographical Memoirs of Fellows of the Royal Society
.
27
: 283?306.
doi
:
10.1098/rsbm.1981.0012
.
JSTOR
769874
.
- ^
Bethe, H. A.
; Winter, George (January 1980).
"Obituary: Otto Robert Frisch"
.
Physics Today
.
33
(1): 99?100.
Bibcode
:
1980PhT....33a..99B
.
doi
:
10.1063/1.2913924
. Archived from
the original
on 28 September 2013.
- ^
"Otto Robert Frisch | Biography & Facts"
.
Encyclopedia Brittanica
. Retrieved
21 December
2023
.
- ^
Frisch, Otto R.; Stern, Otto (1933). "Uber die magnetische Ablenkung von Wasserstoffmolekulen und das magnetische Moment des Protons".
Zeitschrift fur Physik
(in German).
85
(1?2): 4?16.
Bibcode
:
1933ZPhy...85....4F
.
doi
:
10.1007/BF01330773
.
S2CID
120793548
.
- ^
a
b
c
Gribbin, J. (2000).
Q is for Quantum: An Encyclopedia of Particle Physics
. Simon & Schuster. p. 150.
ISBN
978-0-684-86315-3
. Retrieved
4 December
2021
.
- ^
Sullivan, Neil J. (2016).
The Prometheus Bomb: The Manhattan Project and Government in the Dark
. Lincoln:
University of Nebraska Press
. p. 19.
ISBN
978-1-61234-890-2
.
- ^
Rhodes, Richard
(1986).
The Making of the Atomic Bomb
. New York: Simon & Schuster. p. 263.
ISBN
978-0-684-81378-3
.
OCLC
13793436
.
- ^
Hahn, O.; Strassmann, F. (1939). "Uber den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle [On the detection and characteristics of the alkaline earth metals formed by irradiation of uranium without neutrons]".
Naturwissenschaften
(in German).
27
(1): 11?15.
Bibcode
:
1939NW.....27...11H
.
doi
:
10.1007/BF01488241
.
S2CID
5920336
.
The authors were identified as being at the Kaiser-Wilhelm-Institut fur Chemie, Berlin-Dahlem. Received 22 December 1938.
- ^
Meitner, Lise; Frisch, O. R. (1939).
"Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction"
.
Nature
.
143
(3615): 239?240.
Bibcode
:
1939Natur.143..239M
.
doi
:
10.1038/143239a0
.
S2CID
4113262
.
The paper is dated 16 January 1939. Meitner is identified as being at the Physical Institute, Academy of Sciences, Stockholm. Frisch is identified as being at the Institute of Theoretical Physics, University of Copenhagen.
- ^
Frisch, O. R. (1939).
"Physical Evidence for the Division of Heavy Nuclei under Neutron Bombardment"
.
Nature
.
143
(3616): 276.
Bibcode
:
1939Natur.143..276F
.
doi
:
10.1038/143276a0
.
S2CID
4076376
.
The paper is dated 17 January 1939. [The experiment for this letter to the editor was conducted on 13 January 1939; see
Rhodes, Richard (1986).
The Making of the Atomic Bomb
. Simon and Schuster. pp.
263
and 268.
- ^
Otto R. Frisch, "The Discovery of Fission ? How It All Began",
Physics Today
, V20, N11, pp. 43-48 (1967).
- ^
J. A. Wheeler, "Mechanism of Fission",
Physics Today
V20, N11, pp. 49-52 (1967).
- ^
"Fame without a Nobel Prize"
. 5 November 2015.
- ^
"Culture trails – Blue Plaque Guide"
(PDF)
.
University of Birmingham
. Retrieved
4 December
2021
.
- ^
Rhodes, Richard (1986).
The Making of the Atomic Bomb
. Simon and Schuster. pp.
612?613
.
- ^
a
b
c
Frisch, Otto Robert (1980).
What Little I Remember
. Cambridge University Press. pp. 161?162.
ISBN
0-52-128010-9
.
We were building an unusual assembly, with no reflecting material around it; just the reacting compound of uranium-235 ... For obvious reasons we called it the Lady Godiva assembly.
- ^
Rhodes, Richard (1986).
The Making of the Atomic Bomb
. Simon and Schuster. pp.
610
?11.
ISBN
9780671441333
.
- ^
"Here Be Dragons"
.
- ^
r.e. Malenfant (2005).
"Experiments with the Dragon Machine"
.
doi
:
10.2172/876514
.
OSTI
876514
.
S2CID
108799363
.
- ^
a
b
Otto Frisch, "What Little I Remember", Cambridge University Press (1979),
ISBN
0-521-40583-1
Bibliography
[
edit
]
- Atomic Physics Today
(1961)
- Working with ATOMS
(1965)
- What Little I Remember
(1979)
External links
[
edit
]
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