Experience with crystals at Fermilab accelerators

Crystals were used at Fermilab accelerators for slow extraction and halo collimation in the Tevatron collider, and for channeling radiation generation experiments at the FAST electron linac facility. Here we overview past experience and major outcomes of these studies and discuss opportunities for new crystal acceleration R&D program.

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An X-Ray “Laser” at Electron Microscope Voltages?

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010009840x ◽

1981 ◽

Vol 39 ◽

pp. 380-381

Author(s):

J.C.H. Spence ◽

J. M. Cowley

Keyword(s):

Dirac Equation ◽

Fast Electron ◽

Forward Direction ◽

Bloch Wave ◽

Transverse Motion ◽

Relativistic Velocity ◽

Wave Excitation ◽

High Energies ◽

Wave States ◽

Channeling Radiation

There has been much recent interest in the study of channeling radiation (see (1) for a review). In particular, several workers have suggested the possibility of obtaining lasing action from this radiation. Channeling radiation arises in the Bloch wave picture from transitions between bound transverse states of the fast electron. The Dirac equation for the scattering of the fast electron separates into a Dirac equation for relativistic plane-wave states in the forward direction and a Schroedinger equation describing the transverse states. The Bloch wave excitation amplitudes can then be interpreted as occupation indicies and conditions of orientation and voltage found which produce a population inversion. Classically, at high energies the crystal periodicity can be neglected and the radiation treated as arising from an electron travelling at relativistic velocity in the forward direction through a crystal tunnel with the superimposed transverse motion of an harmonic oscillator. Lasing action is obtained as a result of downward transitions between transverse Bloch wave states induced by the photons these generate.

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Above and beyond the content: Feelings influence mental simulations

Behavioral and Brain Sciences ◽

10.1017/s0140525x19003108 ◽

2020 ◽

Vol 43 ◽

Author(s):

Kellen Mrkva ◽

Luca Cian ◽

Leaf Van Boven

Keyword(s):

Mental Representation ◽

Mental Simulation ◽

Past Experience ◽

Prediction Errors

Abstract Gilead et al. present a rich account of abstraction. Though the account describes several elements which influence mental representation, it is worth also delineating how feelings, such as fluency and emotion, influence mental simulation. Additionally, though past experience can sometimes make simulations more accurate and worthwhile (as Gilead et al. suggest), many systematic prediction errors persist despite substantial experience.

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Statistics and parallaxes

International Astronomical Union Colloquium ◽

10.1017/s0252921100073875 ◽

1978 ◽

Vol 48 ◽

pp. 7-29

Author(s):

T. E. Lutz

Keyword(s):

Experimental Design ◽

Statistical Methods ◽

Review Paper ◽

Systematic Errors ◽

Past Experience ◽

Random Errors ◽

Trigonometric Parallaxes ◽

Systematic And Random Errors

This review paper deals with the use of statistical methods to evaluate systematic and random errors associated with trigonometric parallaxes. First, systematic errors which arise when using trigonometric parallaxes to calibrate luminosity systems are discussed. Next, determination of the external errors of parallax measurement are reviewed. Observatory corrections are discussed. Schilt’s point, that as the causes of these systematic differences between observatories are not known the computed corrections can not be applied appropriately, is emphasized. However, modern parallax work is sufficiently accurate that it is necessary to determine observatory corrections if full use is to be made of the potential precision of the data. To this end, it is suggested that a prior experimental design is required. Past experience has shown that accidental overlap of observing programs will not suffice to determine observatory corrections which are meaningful.

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Life Beyond 1MeV

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600000118 ◽

1980 ◽

Vol 38 ◽

pp. 30-33

Author(s):

K.H. Westmacott

Keyword(s):

Electron Microscopy ◽

Past Experience ◽

The Other ◽

Good Case ◽

Other Hand ◽

The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

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