Reuven, born Raymond in 1932 in the Bronx, NYC., was the youngest son of Russian immigrants Bertha and Morris Fox. His mother (born Bracha Rosenfeld) escaped the pogroms in Russia and arrived in Ellis Island in 1928, while his father (born Moshe Fucson) arrived in Ellis Island in 1903.

Raymond followed in the footsteps of his older brother Noel and enrolled in Stuyvesant for high school and then in the City College physics course. He met and befriended Rabi Carlibach (called the dancing Chassidic rabbi) during college.

At age 19 , Raymond met 15yr old Barbara (later Erella) and fell in love. Below is a picture at her sweet sixteen party. The couple married 3 years later and settled in Cambridge, Boston, where Raymond was doing his Ph.D. in physics at Harvard with Nobel Prize winner Norman Ramsey. 

After his Ph.D., Raymond worked at  Lawrence Livermore, where he developed Gamma-ray detection tools and novel plasma sources. During his time in Berkeley, Raymond took up singing seriously and became the main cantor in one of the town's synagogues. 

In 1954 the couple emigrated to Israel, and Raymond did a postdoc at Weizman. He was then invited by Nathan Rozen (former Einstein's students) to help build the physics department at the Technion in Haifa. Raymond and Barbara, now formally named Reuven and Erella then moved North, and before settling in Haifa, spent two years at the kibbutz Shaar Ha-Amakim. 

In 1970, Michal and Merav were born, and in 1972 the family changed their last name from Fox to Fucson. In 1978 the family emigrated to Sao Paulo Brasil, where Reuven became a professor at the University of Sao Paulo and has advised tens of graduate students. Following the diagnosis of Erella with a meningioma, Reuven and Erella joined their daughters in the USA in 2011. 

Reuven studied physics  at the University of New York City, and graduated in 1953.  In 1958 he obtained a doctorate in physics from Harvard University, under the guidance of Nobel prize winner Norman Ramsey.

In 1960 he joined the newly founded Physics Department at the Israel Institute of Technology (Technion). In 1982, he transferred to the Institute of Astronomy and Geophysics at the University of Sao Paulo (IAG), where he worked until his compulsory retirement in 2002. Reuven continued to work as a senior researcher at the institution until 2014. In 2015, he was awarded the title of professor emeritus at IAG. Since 2015 he worked as a staff researcher at Columbia University.

Reuven developed pioneering research on astrophysical plasmas, magnetohydrodynamics and turbulence , cosmology, and studies of the universe.  His work helped unravel several problems regarding accretion disks, galactic winds, star formation, particle acceleration, and dynamos. At the IAG, he supervised 13 doctoral theses and 3 master's dissertations, and 7 other doctorates in Israel.

Throughout his career, he published more than 160 scientific articles in international journals, in addition to abstracts and articles in congresses. He was the creator of a series of conferences, including the New Physics in Space (since 2002) and Challenges of New Physics in Space (since 2008)-see picture.