(b. Vienna, Austria, 29 April 1894; d. Vienna, 27 January 1970), physics, radioactivity, method of nuclear photographic emulsions, photomultiplier technology.
Blau developed the method of photographic emulsions that enabled the recording of tracks of atomic particles and became known for the discovery of “contamination stars,” explosions of atomic nuclei produced by high-energy cosmic-ray particles. She elaborated a theory on the effect of x-rays on biological objects. Using photomultipliers, she designed the first electrically modified scintillation counter and several user-friendly medical instruments for radioactive measurements. She was nominated twice for the Nobel Prize. Blau received the Schrödinger Prize and the Ignaz Lieben Prize of the Austrian Academy of Sciences.
Blau was born in fin de siècle Vienna as the third child of an upper-class Jewish family. Her father, Markus Blau, was a lawyer in the kaiser’s courts and an important music publisher. Her mother, Florentine Goldenzweig, was the sister of Josef Weinberger, the main publisher of Gustav Mahler’s works in Europe. During her childhood, Blau attended some of the best Viennese schools and in 1905 was sent to the private Mädchen Obergymnasium, the only school with official state recognition to prepare women for academic studies. In 1914, when the young men were drafted and women had more access to education, Blau enrolled at the University of Vienna to study physics and mathematics. During the last year of her studies she conducted her Praktikum (practical training) at the Institute for Radium Research, one of the four most important radioactivity research centers in Europe. In 1918, Blau submitted her dissertation on the absorption of diverging gamma rays, and her first paper appeared both in the annual bulletin of the Radium Institute and in the Sitzungsberichte of the Austrian Academy of Sciences.
Blau’s research topic turned out to be important for clinical treatments of cancer. Discovered by a French physicist, Paul Villard, gamma rays had occupied the interest of the radioactivity community since 1900. Because of their penetrating power, which is much higher than that of x-rays, gamma rays proved to be crucial in killing cancerous cells. Eventually, that research topic led Blau to medical physics and to the Laboratory for Medical Radiology at Guido Holzknecht’s clinic in Vienna where she worked as a research assistant after defending her thesis in 1919.
Blau hovered at the boundary of medicine and physics for the rest of her career. In 1921, she left Vienna to accept a position as a physicist in Eppens and Co., which manufactured x-ray tubes in Fürstenau, Germany. A year later she moved to the Institute of Medical Physics in Frankfurt am Main, where she worked as a research assistant. For more than a year Blau instructed doctors in radiobiology, while she conceived and elaborated a theory on the effect of x-rays on biological objects. At that time the Frankfurt Institute was the epicenter of target theory in Germany, which described the impinging of radiation on living tissues as particles hitting a target. The theory’s aim was to use radiation to probe the structure of the organic world. Blau played an instrumental role in developing the statistical analysis of biophysical processes that constituted “hits,” which was the main research project of Friedrich Dessauer, the director of the institute (Beyler, 1997, pp. 39–46). Working with Kamillo Altenburger, she studied the number of “hits” that were entailed in order for a biological process to occur. Her research career in Germany was interrupted abruptly in the fall of 1923 when her mother became ill and she had to return to Vienna. Although she left Dessauer’s laboratory, Blau retained her ties. Later she contributed a piece on photographic investigations of radioactive rays in a multiauthored volume edited by Dessauer on the boundary between physics and medicine (Blau, 1931).
Photographic Emulsions. Between 1923 and 1938, Blau’s research was centered at the Radium Institute in Vienna. Still, when she attempted to obtain a position as Dozentin(instructor) at the University of Vienna, the response was astounding; “You are a woman and a Jew and together this is too much” (Halpern, 1997, p. 197). In the 1920s, the Radium Institute was less conservative than the university, hosting an astonishing number of women researchers and welcoming Jews. During this time, thanks to the Swedish physicist Hans Pettersson, the institute proved to be a major participant in a serious controversy over the artificial disintegration of light elements. The second participant was Rutherford’s laboratory in Cambridge, England. Blau joined Pettersson’s group in Vienna, and with her expertise on the use of photography in radioactivity, she was immediately assigned to develop a new method for tracking charged nuclear particles, that of photographic emulsions.
Rutherford’s discovery of the phenomenon of artificial disintegration by alpha particles prompted the need for more sensitive tools to detect and measure the emitted protons, a need that became urgent during the Vienna-Cambridge controversy.The method of photographic emulsions had been already used by S. Kinoshita and Maximilian Reinganum in the beginning of the 1910s to identify trajectories of alpha particles through emulsions. In early 1924, Blau was assigned by Pettersson to use the same method to observe recoil protons produced by alpha particles in paraffin. With weak radioactive sources she could observe the lower-energy particles, but the accuracy of the measurement was limited. The only strong source available was polonium. To prevent darkening of the plate by gamma radiation, Blau worked with polonium, which was prepared in highly concentrated preparations by Elizabeth Rona, an experienced experimenter at the Institute.
In 1925, Blau detected for the first time the trajectories of slow protons. As the grain thickness of proton tracks was appreciably smaller than that of alpha tracks, it was evident to her that the photographic conditions (emulsion characteristics and development conditions) would have to be improved if high-energy protons—with smaller ionization thickness—were to be observed. In the following years, the method was applied to the disintegration of various atoms and detected the tracks of faster protons. Blau also improved the quality of the processing techniques and emulsions and was able to increase the thickness of the emulsion layers. However, what proved to be decisive for Blau’s career and for the success of her method was the exposure of the emulsions to cosmic radiation. In this achievement, Blau’s collaborator was Hertha Wambacher.
Nine years younger than Blau, Wambacher entered the institute as a Praktikum student, having Blau as her main but informal advisor in her dissertation on the impact of photographic desensitizers on the imprints of alpha, beta, and gamma rays on photographic plates. As Wambacher proved, a major desensitizer of photographic emulsions was the organic dye pinakryptol yellow. In June 1932, the two women coauthored their first paper. Just five months after James Chadwick’s discovery of the neutron, Blau and Wambacher were able to detect photographically protons liberated by unseen neutrons. These protons did not leave an imprint unless the photographic plates were desensitized by means of pinakryptol yellow.
As a consequence of this first success in photographically detecting the ionization protons and explaining the effect of desensitization, Blau was invited by the German photographic giant Agfa, “as their guest of honor,” and a medal was bestowed upon her by the Photographic Association (Blau, curriculum vitae). Additionally, in the fall of 1932, Blau received a scholarship from the Association of Austrian Academic Women to spend six months at Robert Pohl’s physics institute in Göttingen and the rest of her stipendium time at Marie Curie’s Institut du Radium in Paris. But during Blau’s absence from her home institute, Wambacher teamed with Gerhard Kirsch—a Viennese physicist, a Nazi, and Pettersson’s main collaborator—on an investigation of neutrons from beryllium, using Blau’s photographic method. On Blau’s return in 1934, both the institute and Vienna had changed, affected profoundly by the political upheavals of 1933.
Political Unrest. In the context of the wider European political crisis and Hitler’s rise to power in Germany, the political situation in Vienna became increasingly unstable.
The socialists lost power and control of the city in 1934,
Living rise to Austrian fascists and to the Nazis consequently. After her return from Paris, Blau continued her collaboration with Wambacher under an obvious political tension within the institute.
The two women worked on two fronts. First, they improved the emulsion technique by thickening the photographic plates to allow a better deposit of the particle tracks. Ilford, the English photographic company, offered to produce sufficiently thick plates, and Blau suggested that new development methods had to be created. Second, while still struggling to alter their apparatus to suit their experimental needs, Blau and Wambacher applied the photographic technique to neutron studies. Their collaboration turned out to be threatening for Blau’s existence at the institute. In June 1934, Wambacher joined the National Socialist Party and around that time became intimately involved with an ardent Nazi, Georg Stetter, assistant at the Second Physics Institute of Vienna and member of Pettersson’s group.
Continuing their cooperation, in 1936 the two women exposed their emulsions on the Haferlekar, a mountain near Innsbruck, for four months in order to secure high-intensity radiation. Their research project consisted in determining the existence of heavy particles such as protons, neutrons, and alpha particles in cosmic rays, which at the time was considered quite doubtful.
Upon first examination of the plates, they observed proton tracks longer than anyone else had at that time. Yet, to their surprise, Blau and Wambacher observed in the emulsion a “contamination star” (several tracks emanating from a point) that could neither be explained by irregularities in the emulsion nor by unknown radioactive products during the handling and storage of the plates in the laboratory. The assumption was that the large “stars” originated from the disintegration of heavy particles, probably bromine or silver, and that the smaller ones originated perhaps from light elements in the gelatin. Given the theoretical limitations of nuclear physics of the time, the two women could not determine the nature of the primary particle and the exact process of the disintegration. These impressive results, which American historian Peter Galison considers the first “golden event” using emulsions, provoked the interest of the scientific community (1997, p. 44). In 1937, on the basis of their discovery, Blau and Wambacher were awarded the Ignaz Lieben Prize of the Austrian Academy of Sciences.
While the two women were preparing a publication, Stetter approached Blau. He accused her of being unfair to Wambacher and expected her to change the order of the names on their publication since Wambacher was, after all, he argued, the first to look into the microscope and find the star. Blau refused. In the midst of the world’s serious political upheavals and Blau’s tenuous position, Ellen Gleditsch, a Norwegian expert on radioactivity, took a personal interest in her situation and offered her a temporary position as a research assistant in her laboratory in Oslo. Under the enormous pressure from her own ex-advisee and Stetter, Blau rushed to arrange research matters with Wambacher, an arrangement which was a total defeat for her.
As the agreement went, Wambacher, in collaboration with Gustav Ortner, another Nazi at the institute, were going to investigate the relation of the grain and density of the tracks recorded on the photographic emulsions to the energy of the particles produced by them. By measuring the grain thickness of the tracks one could even estimate the energy of the particles that were not brought to rest in the emulsion but passed through. This process had the potential of identifying the particles and the total energy released in the process, the two key points of Blau’s and Wambacher’s earlier work. Blau agreed to continue the absorption experiments, a less promising and more tiresome task. Luckily, she left Vienna on a 7:00 a.m. train to Oslo a day before the Germans paraded triumphantly into Austria on 12 March 1938.
Exile. While Blau knew that she could only remain in Oslo for a limited time, Berta Karlik, a young colleague then and later director of the Radium Institute, encouraged Pettersson to reclaim the instruments he brought to Vienna in the early 1920s. Given the simplicity of the photographic emulsions method and its tabletop scale, portable objectives and microscopes could, at least temporarily, ensure Blau’s research prospects.
In November 1938, after Albert Einstein’s recommendation, Blau left Norway to accept a position at the Polytechnic School in Mexico City. On her way to Mexico the Gestapo confiscated her scientific notebooks, forcing her zeppelin down in Hamburg. She later speculated that those ended up at the hands of her Nazi colleagues in Vienna. However, with or without Blau’s scientific notebooks, Wambacher continued to use the experimental facilities of the Radium Institute. Within two weeks of the Anschluss, she was promoted to the position of assistant at the First and Second Physics Institutes. Publications in major German journals accompanied her rapid promotion in the university ranks. On the contrary, from 1940 to 1944, Blau centered her work in Mexico, deeply frustrated by the lack of research opportunities and by the teaching overload. Only through the efforts of the Jewish community in Mexico, was she able to enter the United States in May 1944.
Photomultipliers and Scintillation Counters. Blau was one of the first to suggest the use of a photomultiplier in combination with a scintillation counter. The original scintillation counter consisted of a thin glass plate spread with an equally thin layer of zinc sulfide. When the plate was struck by charged particles, the screen produced light flashes that were observed through a microscope specifically designed to increase their brightness. The instrument had extensively been used at the Radium Institute during the Cambridge-Vienna controversy. Working for competitive industrial corporations after the Second World War, Blau sought possibilities for professional existence by saving and modifying an old-familiar technique; her past secured her present.
In the physics department of the International Rare Metals Refinery, her first position in the United States, Blau teamed up with B. Dreyfus in combining the use of a photomultiplier tube to a scintillation screen for the measurement of alpha ray sources (Blau and Dreyfus, 1945). Putting together a fluorescent screen with the photomultiplier, which took a very small amount of light and converted it into an amplified electrical signal, and using strong polonium sources, Blau and Dreyfus had in fact described the first electrically modified scintillation counter. As the references to Elizabeth Kara-Michailova’s and Berta Karlik’s work show, both colleagues in Vienna, Blau was the driving force in designing the device. In 1933, after abandoning the ordinary scintillation counter, Karlik had worked on the determination of alpha particle ranges utilizing a photoelectric cell, a sensitive electric device for the detection of the scintillations that replaced the fragile and unreliable human optical system. Karlik’s method, however, was seldom used, as Blau explained, given the limited range of measurements of the ordinary photocells and the lack of adequate and constant alpha-sources. Thanks to the multiplier phototube, Blau overcame the earlier difficulties.
Through her hybrid instrument Blau sought to merge the competing prewar and postwar cultures in physics research. The shift from the ordinary photocells to photomultipliers, in Blau’s experimental practice, was not just a simple replacement of two pieces in an instrument.
The transformation was a deeper, conceptual one for both the experimenter and the instrument. From a research-oriented position in the Radium Institute in Vienna, Blau’s occupation shifted to industrial physics in the post-war United States. The corporations that she worked for 1944 to 1948 were deeply involved in the manufacture of nuclear weapons, the commerce of uranium and radium, and the industrial uses of radium. In the beginning of 1948, Blau moved to the Gibbs Manufacturing and Research Corporation and with J. R. Carlin she worked on industrial applications of radioactivity. Her creative time and efforts were taken up by a number of radioactive devices such as resistors, electrostatic voltmeters, leveling systems, and micrometers.
In her effort to find a decent research position, Blau moved again within the next few months, this time to the Canadian Radium and Uranium Corporation. Carrying over her knowledge in medical physics to the Radium Corporation, Blau designed a photomultiplier scintillation counter for medical use. Designed for “persons not very familiar with radioactive measurements,” Blau’s scintillation counter was a convenient and practical instrument for wide use in hospitals and medical laboratories (Blau and Smith, 1948, p. 68). Despite the fact that she was the first to design and suggest medical applications of the photo-multiplier scintillation counter, Blau remained peripheral and isolated in the competitive world of industrial physics.
In 1950, she moved to the Brookhaven National Laboratory where she had restricted access to the high-energy physics facilities. Remaining faithful to the experimental tradition of the 1930s, Blau was unable to continue her research in the new settings of big science. Although Erwin Schrödinger nominated Blau and Wambacher for a Nobel Prize based on their pioneer work on photographic emulsions in this same year, the Nobel Prize committee almost unanimously intended to give the prize to someone who was doing follow-up work to the previous year’s prize winner, Hideki Yukawa, on the existence of mesons. While the committee recognized the importance of Blau’s contributions, the prize was eventually awarded to the physicist Cecil Powell, who had adapted Blau’s method to his industry-like laboratory in Bristol and turned it to a powerful tool for making “foundational discoveries concerning mesons and their properties” (Nobel Committee Report, 1950).
Return to Vienna. Because of prolonged exposure to radioactivity, in the late 1950s, Blau developed cataracts, requiring an operation. In the dusk of her life facing financial and health problems, Vienna seemed the most suitable destination. She finally returned in 1960. A number of old colleagues tried to gather funds for her and Schrödinger put her up for the Schrödinger Prize, which she received in 1962. Poor, disconnected from any major scientific network, and bitter about several members of the Radium Institute for reaccepting the Nazi Stetter as one of the heads of the Physics Institute after the end of the war, Blau distanced herself from serious research and from old friends such as Karlik. She died on 27 January 1970, in the intensive care ward of the Lainz hospital, lonely and unknown to the international physics community.
WORKS BY BLAU
“Über die Absorption divergenter-Strahlung.” Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften in Wien, Mathematisch-naturwissenschaftliche Klasse, Abteilung 2a, 127 (1918): 1253–1279.
With Kamillo Altenburger. “Über einige Wirkungen von Strahlen.” Zeitschrift für Physik 12 (1922): 315–329.
“Über photographische Untersuchungen mit radioaktiven Strahlungen.” In Zehn Jahre Forschung auf dem physikalischmedizinischen Grenzgebiet, edited by Friedrich Dessauer. Leipzig, Germany: Georg Thieme, 1931.
With Hertha Wambacher. “Disintegration Processes by Cosmic Rays with the Simultaneous Emission of Several Heavy Particles.” Nature 140 (1937): 585.
Curriculum Vitae. 1941 (unpublished). Grenander Department of Special Collections and Archives, State University of New York at Albany.
With B. Dreyfus. “The Multiplier Photo-Tube in Radioactive Measurements.” The Review of Scientific Instruments 16 (1945): 245–248.
With J. R. Carlin. “Industrial Applications of Radioactivity.” Electronics 21 (April 1948): 78–82.
With J. E. Smith. “Beta-Ray Measurements and Units.”Nucleonics 2 (June 1948): 67–74.
Beyler, Richard. “‘Imagine a Cube Filled with Biological Material’: Reconceptualizing the Organic in German Biophysics, 1918–1945.” In Fundamental Changes in Cellular Biology in the 20th Century, edited by Charles Galperin, Scott F. Gilbert, and Brigitte Hoppe. Proceedings of the 20th International Congress of History of Science, Liège, Belgium 20–26 July 1997. Turnhout, Belgium: Brepols, 1999.
Galison, Peter. “Marietta Blau: Between Nazis and Nuclei.” Physics Today 50 (1997): 42–48.
Halpern, Leopold. “Marietta Blau: Discoverer of the Cosmic Ray‘Stars.’” In A Devotion to Their Science: Pioneer Women in Radioactivity, edited by M. Rayner-Canham and G. RaynerCanham. London: McGill-Queen’s University Press, 1997.
Lindh, Axel. “Nobel Committee Report on Marietta Blau and Hertha Wambacher.” Uppsala 1 July 1950 (unpublished). Nobel Archive of the Center for History of Science, The Royal Swedish Academy of Sciences. Stockholm.
Rentetzi, Maria. “Gender, Politics, and Radioactivity Research in Interwar Vienna: The Case of the Institute for Radium Research.” Isis 95 (2004): 359–393.
Rosner, Robert, and Brigitte Strohmaier, eds. Marietta Blau—Sterne der Zetrümmerung. Wien: Böhlau Verlag, 2003. Includes a complete list of Blau’s publications.