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| A Weblog Listing Some of Our Research Results which may be quoted as a valid Net Publication establishing priority claim to new discoveries relative to Radiation Effects in Solids, Nanotechnology, and other fields of research. This is to indicate to all readers of this site that, from time to time, there will appear items relating to the humanities, the arts, and literature which have no apparently immedate direct relation to science and technology. We do not believe that the bridge between the so-called "two cultures" cannot be crossed - rather that there is an intrinsic and wide symbiosis. Entries of this kind will usually be obvious - but some simple word or phrase should make the difference plain - such as - "Consider This!" - or - "Another Thought!" |
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And then: The de Chaddertons emerge from the de Traffords in Chadderton, near Oldham, England. | ||
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| LAWRENCE CHADERTON This divine was a staunch Puritan, brave and godly, learned and laborious, full of moderation and the old English hardihood. He was born at Chaderton in Lancashire, in the year 1537. His family was wealthy, but bigotted in popery, in which religion he was carefully bred. Being destined to the bar, he was sent to the Inns of Court, at London, where he spent some years in the study and practice of the law. Here he became a pious Protestant; and, forsaking the law, entered, as student, at Christ's College, Cambridge. Oh that, in a far higher sense, all divinity-students might be trained in Christ's own college, and learn their science from the Great Teacher himself! These changes took place in 1564. Mr. Chaderton applied to his father for some pecuniary aid; but the wrathful old papist "sent him a poke, with a groat in it, to go a-begging" and disinherited his son of a large estate. The son had no occasion to use the begging-poke. His high character and scholarship procured turn much favor; while his mind was sustained by the promises of the Saviour, for whose sake he had "endured the loss of all things." He took his first degree in 1567, and was then chosen one of the Fellows of his College. He became Master of Arts in 1571; and Bachelor of Divinity in 1584. He did not receive the degree of Doctor in Divinity till 1613 when it was pressed upon him, at the time when Frederick, Prince Palatine of the Rhine, who married King James's daughter Elizabeth, visited Cambridge in state. Fuller, remarking upon this matter, writes, "What is said of Mount Caucasus, 'that it was never seen without snow on the top,' was true of this reverend father, whom none of our father's generation knew in the University before he was gray-headed." He made himself familiar with the Latin, Greek, and Hebrew tongues, and was thoroughly skilled in them. Moreover he had diligently investigated the numerous writings of the Rabbis, so far as they seemed to promise any aid to the understanding of the Scriptures. This is evident from the annotations in his handwriting appended to the Biblia Bombergi,* which are still preserved in the library of Emanuel College.''** His studies were such as eminently to qualify him to bear an important part in the translating of the Bible. In 1576, he held a public dispute with Dr. Baron, Margaret Professor of Divinity, upon the Arminian sentiments of the latter. In this debate, Dr. Chaderton appeared to the highest advantage, as to his learning, ability and temper. *(An edition of the Hebrew Bible, printed by Bomberg, at Venice, in 1518.) **(Vita Laurentii Chadertoni, a W. Dillinigham, S. T. P. Cantab. 1700 Pp. 15, 24.) For sixteen years be was lecturer at St. Clement's Church, in Cambridge, where his preaching was greatly blessed. In 1578, he delivered a sermon at Paul's Cross, London, which appears to have been his only printed production. About that time, by order of Parliament, he was appointed preacher of the Middle Temple, with a liberal salary. It was thought best, perhaps, that a flock of lawyers should have the gospel preached to them by one who had been bred to know the sins of their calling. In the year 1584, Sir Walter Mildmay, one of Queen Elizabeth's noted statesmen, founded Emanuel College, at Cambridge. Sir Walter was not supposed to be a very high Churchman, and the Queen charged him with having "erected a Puritan foundation." In reply, he told her, "that he had set an acorn, which, when it became an oak, God only knows what will become of it." And truly, it pleased God, that it should yield plenteous crops of Puritan "hearts of oak;" and afford an abundant supply of that sound, substantial, and yet spiritual piety, which stands in strong contrast with all superstition and formality. Emanuel College chapel by order of the founder, was built in the uncanonical direction of north and south. Nearly a hundred years after, this non-conforming building was punished by the crabbed prelates, who had it pulled down, and rebuilt in the holy position of east and west, agreeably to the solemn doctrine of the "orientation of churches!" Perhaps there was no better way to convert it from the Puritanism wherewith it was infected, than thus to give it first an over turn, and then a half turn toward popery. It is likely, however, that the religious pecularities which long marked this College are to be ascribed less to the position in which the chapel was placed, than to the influence of its first Master. For this important office, Sir Walter Mildmay made choice of Dr. Chaderton. The modesty of the latter made him quite resolute to refuse the station, till Sir Walter plainly told him, "If you will not be the Master, I will not be the Founder." Upon this, Dr. Chaderton accepted the office; and filled it with zeal, and industry, and high repute, for thirty-eight years. Through his exertions, the endowments of the institution were greatly increased, and it became a nursing mother to many eminent and useful men. It was during his mastership of Emanuel College, that Dr. Chaderton was engaged in the Bible translation, in which good work he was well fitted and disposed to take his part." He was a scholar, and a ripe and good one." Having reached his three score years and ten, his knowledge was fully digested, and his experience matured, while "his natural force was not abated," and his faculties burned with unabated fire. Even to the close of his long life, "his eye was not dim," and his sight required no artificial aid... Many years after, in 1622, having reached the great age of eighty-five, this Nestor among the divines resigned the office he had so long sustained. Not that he was even then disqualified for its duties by infirmity; but because of the rapid spread of Arminianism, and the fear that, if the business were left till after his death; a divine of lax sentiments, who was then waiting his chance, would be thrust into the place by the interference of the Court. The business was so managed, that Dr. Preston, the very champion of the Puritans, was inducted as Dr. Chaderton's successor. The vivacious patriarch, however, lived to survive Dr. Preston; and to see Dr. Sancroft, and after him, Dr. Holdsworth, in the same station. This latter incumbent preached Dr. Chaderton's funeral sermon. Dr. Holdsworth used to tell him, that, as long as he lived, he should be Master in the house, though he himself was forced to be Master of the house. The patriarch was always consulted as to the affairs of the College. The most protracted and useful life must come to its end. There have been various accounts of the time of Dr. Chaderton's death, and of the place of his interment. But all mistakes are corrected by his Latin epitaph, which has been found on a monumental stone, at the entrance of Emanuel College chapel and has been translated as follows; Here lies the body of Lawrence Chaderton, D. D., who was the first Master of this College. He died in the year 1640, in the one hundred and third year of his age. ...He was greatly venerated. All his habits were such as inspired confidence in his piety. During the fifty-three years of his married life, he never suffered any of his servants to be detained from public worship by the preparation of food, or other household cares. He used to say, "I desire as much to have my servants to know the Lord, as myself." These things are greatly to his honor; though his regard to the Lord's Day may excite the scorn of some these degenerate times. Dr. Chaderton is described by Archdeacon Echard, as "a grave, pious, and excellent preacher." As an instance of his power in the pulpit, we will close this sketch with an incident which could hardly have taken place any where on earth for the last hundred years. It is stated on high authority, that while our aged saint was visiting some friends in his native county of Lancashire, he was invited to preach. Having addressed his audience for two full hours by the glass he paused and said, "I will no longer trespass on. your patience." And now comes the marvel; for the whole congregation cried out with one consent, "For God's sake, go on, go on!" He, accordingly, proceeded much longer, to their great satisfaction and delight. "When," says Coleridge, "after reading the biographies of [Izaak] Walton and his contemporaries, I reflect on the crowded congregations, who with intense interest came to their hour-and-two-hour-long sermons, I cannot but doubt the fact of any true progression, moral or intellectual, in the mind of the many. The tone, the matter, the anticipated sympathies in the sermons of an age, form the best moral criterion of the character of that age." Let us not be so unwise as to inquire concerning this, "What is the cause that the former days were better than these?" For even now people like to hear such preaching as is preaching. But where shall we find men for the work like those who gave us our version of the Bible? | ||
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| Published in the NTS Newsletter, April 2006 Tracks and Thermal Spikes: A Comment (in which we claim credit for the compound nature of real energetic particle 'spikes', the fundamental need for an atomistic and defect approach, for processes referred to elsewhere as PAPA and DADA, and for identification of the 'sublattice effect' for compound spikes in compound targets - identifying fluorite and apatite in particular.) Note: electron micrograph ommitted Lewis T. Chadderton Research School for Physical Sciences and Engineering Institute for Advanced Studies, Australian National University, Canberra, ACT 0020 . The conclusion reached by Fleischer (2005) – specifically from comparisons of energy loss rates and etching ratios, as well as variable etch sensitivities for fission fragments and alpha particle recoils in muscovite mica – is that ionisation, not heat, is at the root of track formation for fast charged particles. For some of us working in latent track physics the inapplicability in detail of the thermal spike to particle track registration has long been understood. Fleischer’s independent conclusion is therefore welcome. However the volume of published articles in reputable journals which invoke the thermal spike to describe experimental observations for both etched and latent tracks continues unabated. It has also long been evident that the ion explosion spike first so enthusiastically presented (Fleischer et al. 1975) does not itself explain experiment. Some clarification is therefore necessary! And the more so since thermal and ion explosion spikes are frequently considered to be independent models in almost eternal competition. The thermal spike has its origin in the work of the “tube-alloy” sub- research groups of the The Manhattan District Project which culminated in the first nuclear explosion – Trinity – in the Alamogordo desert. Most of the classified AAEC reports are now readily accessible. Among the physicists involved are the names of Brooks, Bohr(s), Seitz and Ozeroff (see Chadderton and Torrens, 1969), though there is anecdotal evidence for Neils Bohr’s consideration of the thermal effect due to energized electrons not long after his Phil. Mag. seminal work on atomic structure and spectroscopy published in 1913, from which his post-war classical Copenhagen paper on the stopping of charged particles of 1948 is in part a natural consequence. History is also responsible for the too prolonged emphasis on the thermal spike. Induced binary fission itself had not long been discovered and the first fission fragment tracks ‘imaged’ so clearly in cloud chambers remained fresh in the mind, especially the rather long paths of delta-electrons ranging out from fragment trajectories. The coupled differential equations of energy loss to the nuclear and electronic systems of molecules in the gaseous target and the agreement of experimental ranges with those calculated from equations of the Bethe/Bloch genre all appeared to present a very convincing picture. It seemed but a simple step to extrapolate to the stopping of fission fragments in condensed matter – specifically single crystals! Many of us in the 1960’s, including myself, were making fundamental assumptions which were tenuous, to say the least. For example: • The energy deposition process is dominantly to the electron system in the first instance. But the transfer of this energy to the nuclear system, though rapid, is not so simple in real condensed matter. • Viewed from the point of classical thermodynamics it became routine to assume immediate appearance of the energy in a continuum target, an initially sharp transverse (sometime truncated) Gaussian temperature distribution spreading radially in space over times ~ 10-11 s, followed by application of the Dulong-Petit law using macroscopic physical heat quantities specific to the target solid. By these means ‘track widths’ could be calculated. • The facts that the energy transfer process was highly transient and non-linear, and that the statistics were not necessarily simple Maxwellian/Boltzmann, were ignored. • A long continuous track was assumed and if condensed matter phase transitions were considered at all then far too much emphasis was placed on a frozen-in amorphous zone defining a central core. • Whilst electron/lattice interaction was understood to be basic to the entire track registration physics the attractive picture of outwardly ranging delta-electrons persisted. The classical picture of a thermal spike was therefore sometimes modified by the relatively arbitrary addition of an easily manipulated electron/lattice coupling factor of some kind (metals, semiconductors, insulators etc.), without much thought being given to this unorthodox grafting of an entirely quantum mechanical atomistic process onto an entirely classical continuum model. • These general ideas were dominant when the highly successful applications of chemical track etching emerged, and were essentially adopted without question by many workers in this new and rewarding field – apart from a period of preference for the ion explosion spike. • In theories of particle solid interactions leading to thermal spike concepts two-body collisions were almost always the basic assumption, consistent with the conservation laws of energy and momentum, and use of a good centro-symmetric model for the ion/atom and atom/atom interaction potentials. Bragg’s Rule for compound targets was always assumed, and anisotropy of crystal lattices ignored. It is curious, in retrospect, that less attention was given to the conservation of charge, since it is by these means that the rapid return of excited electrons to the vicinity of the moving ion can be rationalized and understood, as can the progressive fall during stopping of the projectile effective charge Zeff. – becoming zero at end of range, when thermalised. * * * * * The extension of track physics to applications made by chemical etching of the ‘target’ has been one of its greatest victories – geochronology being a fine example. Advantages include access to tracks in the bulk through optical microscopy, and accurate measurements of track lengths, and their statistical spatial density. Necessarily, however, all other information as to track registration phenomena is lost, though generally a thermal spike is assumed. Latent tracks can be investigated by a number of diagnostic techniques, including high resolution transmission electron microscopy (HRTEM) and channelling–Rutherford backscattering (c-RBS). Note, however, that the information extracted almost exclusively relates to short track segments. It is in interpreting such measurements that so many authors have assumed that the original tracks were continuous, and values drawn down of so-called ‘effective track radii’ as a function of particle properties. Once again a thermal spike is generally assumed, and only bulk macroscopic physical properties of an assumed continuum target are called upon. The two experimental (etching/latent) studies yield different information. What we need is comprehensive and inclusive information at the atomic level as to track lengths, structure, widths (if definable) and the part played by defects at the atomic level. Chemical etching gives us track lengths (projectile ion ranges?). TEM gives us remanent track structure but only for short track segments. There is only one case we know of (Cruz et al. 2003) in which a track structure length and its details to end of range are reasonably well predicted - for 30 MeV C60 cluster ions in yttrium iron garnet, or YIG (Dunlop et al. 1997). The point was made here that it is necessary to understand that the stopping of a C60 cluster ion cannot be described by the simple addition of the effects due to 60 non-interfering carbon ions. Additional corrective forces arise from a collective influence of an induced plasma making for non-linear stopping and so-called vicinage (neighbour) effects. There is insufficient space here to detail all of the cautions which must be exercised. Consummate care, however, must be used in applications of the computer codes TRIM and SHRIM, or any MD simulations for that matter. Note that TRIM does not have a free surface (making calculations of critical energies for track registration doubtful to say the least) – it simulates a continuum and there is therefore no crystallinity (thereby excluding anisotropies due to channelling and energy/momentum focusing). It allows for no specific defects in elemental crystals or sublattices in compound targets, and always assumes the Bragg Rule of Additivity. Thermal effects – spike, transient, or long lasting – cannot be addressed. And important fluctuations in Zeff are totally absent! The example we cite shows that we have coincidentally learned much that is new about single ion tracks in crystals from observations of tracks due to cluster ions, and especially that we must all address the basic assumptions we make in the physics of energetic charged particle stopping whilst it is taking place - during track registration - and afterwards. We find, for example, that for etched fission track work in geological thermochronology studies the basic annealing analysis procedure restricts all to temperature T in the usual Arrhenius expression. And yet experiment – the so-called WVC effect (Wendt et al. 2003) shows that an opposing ambient pressure P (and stress ?) can severely slow down, and even arrest the rate of track shrinkage during annealing in apatite . The WVC effect has been independently verified. But there is no final agreed verdict yet as to what this means for thermochronology, and apatite in particular, though certainly many otherwise convenient minerals (e.g. zircon) are effectively ruled out. Temporal factors associated with long time annealing due to specific ‘point defects’ also cast serious doubt on whether measured old track lengths are actually equivalent to the real fragment range; they are frequently markedly less. In addition the assumed ‘Principle of Equivalent Time’, which asserts that both fossil and induced fission fragment tracks anneal at the same rate, is increasingly found not always to hold up experimentally. Nor are workers in latent track research to be excused some of their basic assumptions, and corresponding interpretations rooted in the simple thermal spike alone. We find using HRTEM that tracks at and near surfaces or subsurfaces (e.g. grain boundaries) are substantially structurally affected by a drain or sinkage of characteristic point defects to nearby surfaces. This entirely new “skin effect” (Chadderton et al. 2006) – which defines new ‘subsurface track’ species - can also put in jeapordy conclusions drawn from c-RBS experiments about effective track widths (there is in general a poor understanding of what the statistical quantity ?min really means), about associated sputtering, and the so-called ‘velocity effect’. For normal thin TEM specimens – with two close surfaces - the skin effect is even more profound. And for sputtering from surface tracks it seems clear that ion explosion spike dominates strictly thermal effects. * * * * * For compound targets there is a very important sub-lattice effect in which, for an ionic binary target such as fluorite (CaF2) for example, the anions preferentially ‘soak-up’ the electronic energy deposited, and for which (see Chadderton, 2003) dominant crystallographic axial movements of the very specific Vk defect can be shown to be responsible for regular intermittent tracks comprising polyhedral calcium colloids. More recently we have re-examined electron micrographs from 1963 of molybdenumtrioxide (MoO3) irradiated with 29.5 MeV He+ ions down a planar channel (see figure) and reconfirmed the generality of the sub-lattice effect. In this much earlier observation the effect is also clearly responsible for the shaping of tracks due to the moving of O- defects, and the simultaneous creation of what are the well-known planar Wadsley defects (rich in oxygen), and central superlattices of molybdenum metal. No macroscopic thermal spike model can possibly describe these observations. It has been known for some time that it is necessary to invoke crystal defects (as is so often the case in condensed matter physics) to explain real track structure both during track registration and post-annealing studies. * * * * * Now we must adopt a more compound spike within which a variety of atomistic mechanisms can operate (Chadderton, 2003). Of course, in the vernacular, it is ‘hot’ when a track is formed. But the thermal spike essentially (and only) offers a didactic distant view of the physics, and a vague semiquantitative estimate of the outward ‘reach’ of a track. Additionally, rather than revert to ‘ionization’ as the critical factor (Fleischer, 2005), we recommend adoption of the more general ‘electron excitation’. This makes way for a compound spike which, whilst including inter alia both thermal and ion explosion features, also allows for the proper inclusion of phenomena based e.g. on the non-radiative ‘self-trapped exciton’, and other fundamental defect mechanisms yet to be discovered. The compound spike is clearly more complex for compound than for elemental targets. References Chadderton, L. T., Rad. Measurements, 36 (2003) 13. Chadderton, L.T., Jonckheere, R., Ewing, R., Khalil, A.S., Weise, C., Wang, L., Ridgway, M.C., Stewart, A.M. and Trautmann , C. submitted to INTS-23, Beijing, September (2006). Chadderton, L.T. and Torrens I. McC. (1965) “Fission Damage in Crystals” (Methuen, London). Cruz, S.A., Gamaly, E., Chadderton, L.T. and Fink, D. Rad. Measurements 36 (2003) 145. Cruz, S.A. and L. T. Chadderton, Rad. Measurements 40 (2005) 765 Dunlop, A., Jaskierowicz, G.,Jensen, J. and Della-Negra S. Nucl. Instruments Methods B132 (1997) 93. Fleischer R. L., INTS Newsletter 5 (2005) 3.Fleischer R.L., Price, P.B. and Walker R. M. (1975) “Nuclear Tracks in Solids: Principles and Applications” (University of California Press, Berkeley”). Wendt, A. S., Vidal, O. and Chadderton, L. T. Earth and Planet Sci. Lett. 593 (2003) 201. /Users/junechadderton/Desktop/torch.gif | ||
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| " O sleep! O gentle sleep! Nature's soft nurse, how have I frighted thee, That thou no more will weigh my eyelids down And steep my senses in forgetfulness?" Henry IV | ||
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| To all of those who, like myself, suffer from this seriously debilitating condition associated with clinical depression, I offer my profound and deepest sympathies. "Chronic Fatigue Syndrome Is Not Your Fault" If you are suffering from the pain, weariness, and depression of Chronic Fatigue Syndrome, you are not at fault. Many doctors want you to believe that your symptoms are psychosomatic, that you’re a hypochondriac, or that you’re depressed. In other words, they tell you that you’re the one with the problem—you’re hypersensitive, just imagining it, or you’re just plain lazy. The fact of the matter is that they are simply wrong. Despite what your doctor might have told you, Chronic Fatigue Syndrome is not only a real health problem, it can have devastating effects on all parts of your life. In fact, if you have Chronic Fatigue Syndrome, it's not something mental, or emotional. Indeed, it’s not your fault at all. The only blame you can take is if you don't do anything about it! If you’re like many Chronic Fatigue Syndrome victims, you don’t know where to turn. You need help, but your doctor just doesn’t seem to be doing enough. ********** How do I know if I might have chronic fatigue syndrome? If you answer yes to any of the questions listed below, you may have chronic fatigue syndrome (CFS), which is also called chronic fatigue immune dysfunction syndrome (CFIDS). Have you been tired (fatigued) for a long time--more than 6 months--even though you are getting enough rest and are not working too hard? Has your doctor been unable to find illnesses that could explain your symptoms? Are you able to do less than half of what you used to do because you feel tired? Have you had problems that keep coming back or don't go away for 6 months or more with four or more of the following signs and symptoms? 1) Unexplained muscle soreness 2) Pain that moves from joint to joint but doesn't include redness or swelling 3) Headaches that are different from the kind you usually get or headaches that make your whole head hurt 4) Trouble with short-term memory or concentration 5) Feeling tired for more than 24 hours after exercise that didn't bother you before 6) Trouble sleeping . What causes chronic fatigue syndrome? No one is certain about what causes CFS. The symptoms may be caused by an immune system that isn't working well. Or they may be caused by some kind of virus. Researchers are looking for the cause of CFS. How is chronic fatigue syndrome treated? The first step is to see if there is a medical cause for your fatigue. Your doctor will probably want to review your symptoms and medical history, and give you a physical exam. Your doctor may also want to do some blood tests, but lab testing is not often helpful. Some of the symptoms, such as muscle aches, sleep problems, anxiety and depression, can be treated with medicine. The medicine can only reduce your symptoms and allow you to be more active, not cure the fatigue. So far, there is no medicine that cures the entire syndrome. Most symptoms improve with time. How can my doctor help ? Your doctor can work with you to provide symptom relief and to help you find ways of coping with the way CFS changes your life. Chronic fatigue affects you physically, emotionally and socially. When you address all of these factors, you have the best chance of adjusting to your illness and feeling more satisfied with your life. If you have CFS, a good long-term relationship with your doctor helps. This relationship can be the key to helping you feel less frustrated. ************** Careful Consideration of Information about CFS Because the cause of CFS has not been identified and its effect on the body is not well understood, periodically new unvalidated beliefs about cures and causes of CFS are widely circulated. These may be based on one or more recent reports from the peer-reviewed scientific literature, or they may evolve from the anecdotal remarks of clinicians or scientists at medical meetings. In some cases the origin is obscure. Even work that is of sufficiently high caliber to be published in the scientific literature is not without limitations and design flaws, and all published work needs to be verified and expanded on by others before it can be applied with confidence in clinical situations. With regard to some stories that are currently circulating about CFS: (i) there is no evidence that CFS patients lose their fingerprints; (ii) there is no scientific evidence of any nutritional deficiency in CFS patients; and (iii) suicides of CFS patients have been reported, but the rate of occurrence has not been well-studied and it is not known whether the rate is higher or lower than what would be expected in the general population. It is not practical to address all of the information that circulates or emerges regarding CFS. Simply be advised to be wary of information that points to sure cures or that alludes to pathological damage as a consequence of CFS. Specific questions should be discussed with the patient's physician, local or state health department, CDC, or one of the national patient support organizations. Fellow sufferers - please do share your experience with me if you have the time - chadderton3@gmail.com ****************** | ||
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| Swift Ion Track Registration, Evolution and Annealing in Indium Phosphide Single Crystals A.S. Khalil, L. T. Chadderton, D. J. Llewellyn, A. M. Stewart, M. C. Ridgway. Research School of Physical Sciences and Engineering, Institute of Advanced Studies, The Australian National University, Acton, Canberra, ACT 0200, Australia Experiments are described in which indium phosphide crystals were irradiated with 200 MeV Au+ (~1MeV/amu) ions. Corresponding primary electronic stopping powers Se are ~ 21.3 keV/nm. Track formation and annealing in thin crystals were studied by Transmission Electron Microscopy (TEM) at ion fluences up to and beyond saturation. For intermediate fluences the ‘bending’ of one track towards a close neighbour, registered earlier, illustrates the central importance of interactive characteristic intrinsic point defect motion, probably in the ‘halo’, in the atomistic physics. High Resolution Transmission Electron Microscopy (HRTEM) shows tracks to have a ‘beaded’ nature with a ‘core’ diameter ~5nm, and that the beads are not amorphous in nature. We do not conclude, however, that either this structure or this dimension is representative of tracks, if any, in bulk InP since path conclusions made on the basis of HRTEM are frought with pitfalls for the unwary and are most frequently not considered. We explain this, and also discuss the structure in terms of instability driven fragmentation of nanoscale fractal islands. Atomic Force Microscopy (AFM) was used to investigate the post irradiation effects on bulk InP surfaces. We find no individual surface tracks. For high fluences - 5x1013-1x1014 ion/cm2. the surface becomes amorphous, and quite dramatically rough. Keywords: Swift ion tracks, point defects, track interactions, TEM, HRTEM, AFM | ||
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| Point Defect Activity in Ion Damage, Track Registration and Annealing in Crystals: The Skin Effect L. T. Chaddertona, R. Jonckheereb, R. Ewingc, A. S. Khalila, C. Weiseb, L. Wangc, M. C. Ridgwaya A. M. Stewarta, C. Trautmannd a Research School of Physical Sciences and Engineering, Institute of Advanced Studies, The Australian National University, Acton, Canberra, ACT 0200, Australia. b Geologisches Institut, Technische Universität - Bergakademie Freiberg, Bernhard-von-Cotta-Straße 2, D-09599 Freiberg (Sachsen) Germany. cNuclear Enginering and Radiation Sciences, University of Michigan, Ann Arbor, MI,. USA 48109. d Gesellschaft für Schwerionenforschung – Materialwissenschaften, Planckstraße 1, D-64291 Darmstadt, Germany. Experiments are described in which Si, GaS, InP, MoS2, MoO3, CaF2 (fluorite), Ca5(PO4)3(OH,F,Cl) (apatite) and (Ce,La,REE)PO4 (monazite) were irradiated with fission fragments and other heavy ions (e.g. 100 keV Au+, 200 MeV Au+ and ~800 MeV U+). Damage, including latent track structure and annealing due to heat and electron irradiation were characterized using Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM), Atomic Force Microscopy (AFM), and track etching. We find that latent track structure in thin crystals - morphology, intermittencies, characteristic distances and dimensions - depends upon a rapid drain of characteristic point defects - track to track, to surfaces, interfaces, or extended defect sinks. This accords with the atomistic transient compound spike [1]; not the macroscopic equilibrium thermal spike. In traditional studies of low energy ion implantation, loss of point defects leads to a surface damage depleted zone. For swift ions, it gives rise to a “skin effect”. Latent tracks differ from bulk tracks and are pinned to the surface/ interface, which constitutes a track retentive zone. Our results demand consideration of the intermediate class of sub-surface tracks. There are important implications for c-RBS and the velocity effect, and for a widespread recognition of the limits of SRIM. There is the prospect of a new experimental ‘point defect spectroscopy’. Latent track structures in insulating monazite and apatite are similar to those in fluorite, and originate in the anion “sublattice effect” [2]. Chemical etching studies show fission and high energy ion tracks in unannealed monazite to have lengths (ranges) much less than those predicted by SRIM, due to the partial point defect stimulation of projectile assisted prompt anneal (PAPA) by homoepitaxy. Tracks in bulk apatite are not evidently amorphous, but appear to have a pseudo-monazite structure prior to annealing. A reassessment of geological applications of track annealing is recommended. Keywords: Sub-surface swift ion tracks, skin effect, compound spike, point defects, track interactions, TEM, HRTEM, AFM, RBS and SRIM, monazite, apatite, sub-lattice effect. Corresponding author: Lewis. T. Chadderton Email: lewis.chadderton@anu.edu.au | ||
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