Cosmic Ray and High Energy Physics

High Energy Particle Research at DIAS and CERN

Fig 1 | D O'Sullivan Monitoring K-Minus Interactions at CERN in 1964
Professor O'Sullivan's research work on K-mesons and hypernuclei was carried out between 1961 and 1968 as a member of the K Minus Collaboration under the direction of Prof Eric Burhop FRS of University College London. Colleagues at DIAS included Alex Thompson and Tara Shah. Periods were spent at CERN carrying out experiments with the first high energy K-meson beams. This work resulted in new information on proton-meson scattering, the discovery of new hypernuclei and lambda particle nuclear binding energies as well as the discovery of the first double hypernucleus. Figure 1 shows D O'Sullivan monitoring K-Meson interactions at CERN in 1964.

In 2000/2001 he led a major campaign with Dr Nigel Buttimore on behalf of the Royal Irish Academy to encourage the Irish Government to join CERN. It was supported by many Irish and international scientists and included exploratory discussions with CERN personnel including its Director Professor Luciano Maiani, and Professor John Ellis, Chief Theorist, in Dublin and Geneva and several meetings with Irish Government officials throughout the campaign. The photograph below shows (from left) Prof John Ellis, Prof Luciano Maiani, Prof Denis Weaire, Denis O'Sullivan and Dr. Don Thornhill at one of these meetings at The Royal Irish Academy.

Nuclear Track Research at DIAS,General Electric(GE) Research Laboratories,Schenectady and Berkeley University

Fig 2 | D O'Sullivan at Berkeley in 1970
Following the discovery of the nuclear track detection method by Price, Fleischer and Walker in the mid-sixties and the failure of Ireland to join CERN, Professor O Ceallaigh encouraged the group at DIAS to pursue alternative methods of nuclear particle and cosmic ray research. This resulted in a very successful collaboration between GE and DIAS where the expertise of each group was combined to advance the application of the nuclear track method to space and nuclear particle research. When Buford Price was appointed Professor at Berkeley in 1969 he invited D O'Sullivan to join him in setting up a new laboratory there and to lecture and undertake research. 

Work carried out on lunar material collected by Neil Armstrong and the crew of Apollo-11 and investigation of ultraheavy cosmic rays by high altitude balloon flights were included while at Berkeley. A proposal for a joint DIAS-Berkeley cosmic ray experiment on the Moon during upcoming Apollo-16 Mission was submitted successfully to NASA by Price and O'Sullivan during this period.

Apollo-11 Mission to the Moon

Following the successful Apollo-11 Mission to the Moon in 1969 (Figure 3, courtesy of NASA), Price and O'Sullivan received some of first lunar material for scientific investigation at Berkeley. 

Fig 3 | Apollo-11 Mission to the Moon 1969(courtesy of NASA)
Studies of the tracks of galactic iron group cosmic ray nuclei in the interior of rocks 10003 and 10017 indicated exposure on the lunar surface for approximately ten million years. Measurements of the steep gradient of these tracks was related to the lunar erosion rate and the average energy spectrum of solar flares over the last ten million years. Preliminary searches were made for the presence of tracks of hitherto undiscovered magnetic monopoles without success. Results were published in the Proceedings of the Apollo-11 Lunar Science Conference in Houston, Texas, in January 1970.

Apollo-16 Mission to the Moon

Fig 4 | Apollo-16 on the Lunar Surface in 1972(courtesy of NASA)
A proposal by Price and O'Sullivan to carry out a cosmic ray experiment on the Moon was chosen by NASA as part of the Apollo-16 Mission in1972. This DIAS-Berkeley experiment was the first Irish space experiment and is described as 'Ireland's first direct space science participation' in the The European Space Agency's' Short History of Irish Space Activities' (ESA Publication HSR-40,September 2008). O'Sullivan was to participate in a total of sixteen missions between 1969 and 2012.

Figures 5 and 6 (courtesy of NASA) show the frame holding the cosmic ray detectors attached to the lunar module as it descends on to the lunar surface and later, resting against a leg of the module as it is exposed on the Moon.    

Fig 5 | The Detectors resting against the leg of the module on the LunarSurface(courtesy of NASA) 

Fig 6 | The Cosmic Ray Detectors Attached to the Lunar Module as it Descends on
the Lunar Surface(courtesy of NASA)

The experiment was the first to measure the charge spectrum of such low energy cosmic ray nuclei outside the Earth's magnetosphere and on the lunar surface and determine their origin and to undertake some of the earliest investigations of energetic solar particles on the Moon. O'Sullivan worked with Price on the preliminary analysis at Berkeley in the summer of 1972 and later returned to Dublin to undertake responsibility for the charge abundance investigations and worked with his colleague Alex (Archie) Thompson.

Space Shuttle Launches the LDEF in 1984

A major study of the composition and origin of cosmic ray nuclei with charges greater than 70 up to and beyond Uranium, was proposed by O'Sullivan and Thompson as principal investigsators in 1976 and selected in an international competition by NASA for launch aboard the Shuttle Challenger in 1984.The team included Cormac O Ceallaigh of DIAS and K.P.Wenzel and V.Domingo of ESTEC,the Netherlands. It was the largest experiment of its kind to be launched by the Shuttle and remained in Earth orbit for 69 months.It collected the world's largest sample of cosmic ray actinide elements to date. Figure 7 shows the LDEF in Earth orbit.  
Fig 7 | The LDEF in Earth Orbit.The DIAS/ESTEC Experiment Occupied 20% of the
Spacecraft's Area(courtesy of NASA)
Analysis continued for an extended period and a number of post graduate students and other staff at DIAS also worked on the project including J.Donnelly, A.Keane, J Bosch, R.Keegan and Prof L Drury.

O'Sullivan watches the LDEF launch at Cape Kennedy aboard the Challenger Shuttle and relaxes after the successful start of the Irish-ESTEC Mission.
D O'Sullivan and A Thompson are shown below with Challenger pilot jim Wetherbee and Bonnie dunbar, mission specialist, following the successful recovery of the LDEF. Unfortunately, both the Challenger and Discovery Shuttles which launched and recovered the LDEF, respectively, were lost in tragic accidents later.

Missions to Halley's Comet and Comet Gregg-Sjellerup and Planet Mars

Fig 8 | The Giotto Spacecraft with the Irish/German Instrument on Board(courtesy
of ESA)
O'Sullivan,Thompson and B.Jordan comprised the DIAS team in two major ESA missions to Halley's Comet,Comet Gregg-Skjellerup and the Soviet PHOBOS mission to Mars between 1987 and 1992.These were joint collaborations with St Patrick's College Maynooth,The Max Planck Institute,IKI Moscow and the Budapest group.

These experiments included the first in-situ measurements of solar particle interactions in a cometary environment,detailed investigations in the martian atmosphere and the first joint Soviet/Western collaboration in the field. Figure 8 shows the Giotto spacecraft with the Irish/German instrument on board and Figure 9 shows the Soviet Phobos spacecraft.

Fig 9 | The Phobos Spacecraft before Launch to Mars(courtesy of NASA)
D O'Sullivan and the International Space Station

Following the launch of the International Space Station in 1999 new opportunities opened up for many scientists.O'Sullivan was invited by NASA to carry out experiments related to the exposure of humans to cosmic rays in Earth orbit. With his post doctoral colleague, Dazhuang Zhou, he made the first measurements of the charge spectrum of cosmic ray nuclei from helium to iron in the Space Station orbit on the STS-108 mission in 2001 and followed with further experiments on STS-112 and ISS-7S between 2002 and 2003. These high energy particles penetrate the spacecraft walls and living quarters of astronauts and produce further nuclear interactions which can cause cancer in humans.

In order to investigate the impact of space radiation on sensitive human organs, the European Space Agency developed an international facility called 'Matroshka' which was co-ordinated by the German Space Agency (DLR) in Cologne. D O'Sullivan and his team were chosen to investigate the impact of ultra-heavy nuclei on human tissue in space. 

A torso, (see Figure 10), 
Fig 10 | The Matroshka Phantom (courtesy of ESA)
designed to simulate a human body and made of tissue equivalent material was exposed inside and outside (Figure 11), the Space Station over a number of years between 2005 and 2008 and DIAS detectors were located at the kidney, stomach and skin locations. 

Fig 11 | The Matroshka Exposed Outside the Space Station(courtesy of NASA)

The data was used to estimate the impact of cosmic rays and energetic solar particles on astronauts on extravehicular (EVA) activities and when inside the living quarters. The Russian expendable spacecraft, Progress,was used to ferry the detectors into orbit (Figure 12). 

Fig 12 | The Progress Spacecraft(courtesy of NASA)
In a collaboration with the Belgian Nuclear Research Centre and the Czech Academy, O'Sullivan and colleague D Zhou investigated the effect of cosmic radiation in space on bacteria ,using the International Space Station (DOBIES project) in 2003, 2004 and 2008. 

Fig 13 | The Russian Soyuz Spacecraft(courtesy of NASA)

The Russian Soyuz craft (Figure 13), was employed on two of these occasions. Cosmic rays can cause damage to DNA in humans and bacteria. Bacteria are important on space missions for recycling waste. They can also undergo unwelcome mutations in long term missions. The ESA Columbus Laboratory was employed for these experiments (Figure 14).
Fig 14 | The ESA Columbus Laboratory(courtesy of ESA)

Preparing to go to Mars-The Theseus Project

Cosmic radiation is considered to be the main health hazard for human exploration and colonisation of the Solar System. The European Space Agency and the European Science Foundation selected a group of specialists to investigate and propose solutions to the various difficulties involved in future space travel, with particular emphasis on a voyage to Mars. D O'Sullivan was appointed to the Space Radiation Group and the photograph shown (Figure 15) here was taken at one of their meetings in the Black Forest in 2009. The final 'road map' was published in 2012.

Fig 15 | The Theseus Mars Space Radiation Team
Search for Ultraheavy Nuclei Using High Altitude Balloons (1970s)

Prior to the availability of spacecraft for the investigation of cosmic rays and their component at the upper end of the periodic table ( up to Uranium and beyond ), the DIAS group including O Ceallaigh, O'Sullivan and Thompson, collaborated with P.H. Fowler of Bristol University in flying very large volume balloons (close to the size of a football stadium when fully expanded at the top of the atmosphere) over North America in the seventies. These experiments provided some of the first statistically significant samples of these nuclei and allowed a preliminary comparison with theoretical estimates of their source and nature.

Exposure of Aircrew to Galactic Cosmic Radiation

Due to the growing concern over the exposure of aircrew to galactic cosmic rays and high energy solar particles, the European Commission funded an extensive investigation of the problem over a full eleven year solar cycle from 1995 to 2006 and D O'Sullivan was appointed to co-ordinate the project. This research work included DIAS and ten other European laboratories along with CERN and assistance from NASA and many international airlines. It was the first investigation of the exposure of aircrew to cosmic radiation and solar energetic particles as a function of latitude, altitude over a complete solar cycle. Real time data was also recorded in flight during a significant solar flare event. The photograph below shows scientists attending a meeting at DIAS hosted by Prof O'Sullivan, with Dr Zhou (front row, second left) and Eileen Flood, scientific secretary (centre).