collimation

Definitions

  • WordNet 3.6
    • n collimation the accurate adjustment of the line of sight of a telescope
    • ***
Webster's Revised Unabridged Dictionary
    • n Collimation The act of collimating; the adjustment of the line of the sights, as the axial line of the telescope of an instrument, into its proper position relative to the other parts of the instrument.
    • ***
Century Dictionary and Cyclopedia
    • n collimation The accurate adjustment of the line of sight of a telescope. A telescope having only one motion, as a meridian instrument or a surveyors' level, is in collimation when the mean of the wires or other assumed point apparently traverses a great circle of the heavens when the telescope is rotated. The error of collimation, or the distance of the small circle actually described, when the line of sight is not accurately adjusted, from the parallel great circle, is also familiarly called the collimation. It is measured by reversing the telescope in its bearings and measuring half the angular distance between the two objects thus successively brought to the mean position of the wires. Two telescopes are said to be in collimation when their optical axes coincide.
    • ***
Chambers's Twentieth Century Dictionary
    • n Collimation kol-li-mā′shun the adjustment of the line of sight of a telescope
    • ***

Etymology

Webster's Revised Unabridged Dictionary
Cf. F. collimation, fr. a false reading (collimare,) for L. collineare, to direct in a straight line; col-, + linea line. Cf. Collineation
Chambers's Twentieth Century Dictionary
L. collimāre for collineāre, to bring into line with—col, together, linea, a line.

Usage

In literature:

The collimator and observing telescope have an aperture of 25 mm., focus of 200 mm.
"Astronomical Instruments and Accessories" by Wm. Gaertner & Co.
Whenever the position is changed, the mirrors have to be re-collimated.
"Photographs of Nebulæ and Clusters" by James Edward Keeler
This lens was called the "Collimating" lens.
"The Progress of Invention in the Nineteenth Century." by Edward W. Byrn
***

In news:

Flexible Collimation technology improves cardiovascular X-ray imaging.
***

In science:

Neutron cross sections needed especially for (a) H, C, and O (most abundant in body tissue), (b) Si (shielding material and detectors), (c) N and P (present in tissue and bones), (d) Ca (present in bones), and (e) Al, Fe, Cu, W and Pb (collimation, beam shaping, shielding).
Simple functional forms for total cross sections from neutron-nucleus collisions
Most of the cool gas is accelerated to nonrelativistic high velocities, vj ≃ 103 − 104 km s−1 , after flowing through, or close to, an accretion disk around the central black hole. A poorly collimated wind (or double not-well collimated opposite jets) is formed.
Feedback Heating with Slow Jets in Cooling Flow Clusters
We shall conclude that the best agreement with the available data occurs if the jets are not well collimated.
Feedback Heating with Slow Jets in Cooling Flow Clusters
In the present paper we extend this idea of slow and massive not-well collimated jets, and incorporate it to be an important ingredient in the duty-cycle of the moderate CF model.
Feedback Heating with Slow Jets in Cooling Flow Clusters
From Equations (4) and (6) we see that the large opening angle of the jet (hence termed here a not-well collimated jet) facilitates bubble formation (Soker 2004a).
Feedback Heating with Slow Jets in Cooling Flow Clusters
On the other extreme, a slow jet can be well collimated, hence propagates along a narrow cone into the ICM.
Feedback Heating with Slow Jets in Cooling Flow Clusters
But what is the reason for the sharp transition from a well collimated jet to radio lobes in Hydra A? We note from the last equation that a slow jet, even if weak, might stay supersonic to large distances.
Feedback Heating with Slow Jets in Cooling Flow Clusters
We propose, therefore, that the current jets in Hydra A were preceded by collimated slow and dense jets which opened a tunnel to a distance of r ∼ 5 kpc, through which the current jets are expanding almost undisturbed.
Feedback Heating with Slow Jets in Cooling Flow Clusters
When the current jets leave these tunnel, they interact with the ICM, become subsonic, and lose their collimation. A slow jet with these parameters ( ˙E = 1043ergs−1 and vj = 3000 km s−1 ) has a mass loss rate of 3.5 M⊙ yr−1 , namely, the two proposed slow jets blow ∼ 7 M⊙ yr−1 back to the ICM.
Feedback Heating with Slow Jets in Cooling Flow Clusters
We found that the wave transmission always tends to be guided or collimated into the ΓM direction, independent of the incident angles or the orientation of the Γ − M direction.
About negative refraction and left handed materials
The aperture is defined by active collimators made from tubes of slow plastic scintillator. A similar modular polarimeter can be found as GRAPE [21,22], which is optimized for measuring polarization of energy ≥ 100 keV from solar flares and gamma-ray bursts.
Beam Test of a Prototype Detector Array for the PoGO Astronomical Hard X-Ray/Soft Gamma-Ray Polarimeter
To simplify readout, the instrument is organized as an array of hexagonal phoswich units, each consisting of a fast scintillator (decay time τ ∼ 2 ns), a slow plastic scintillator active collimator (τ ∼ 300 ns), and a bottom BGO anti-coincidence detector (τ ∼ 300 ns), all viewed by a single photomultiplier tube (PMT).
Beam Test of a Prototype Detector Array for the PoGO Astronomical Hard X-Ray/Soft Gamma-Ray Polarimeter
In order to reduce the background due to downward atmospheric gammas and cosmic diffuse gammas coming from outside the field-of-view, we also use a thin high-Z metal foil, wrapped around the active collimator tubes, as passive collimators.
Beam Test of a Prototype Detector Array for the PoGO Astronomical Hard X-Ray/Soft Gamma-Ray Polarimeter
Tests with slow scintillator collimators and bottom/side BGO scintillators and with larger number of units will be done in fiscal year of 2005 and 2006.
Beam Test of a Prototype Detector Array for the PoGO Astronomical Hard X-Ray/Soft Gamma-Ray Polarimeter
In spite of the significance of the MeV gammaray imaging in Astronomy and Medical imaging, the quality of MeV gamma-ray images obtained with existing cameras, such as a position-sensitive detector with a collimator and classical Compton imaging , are not adequate yet.
Development of an advanced Compton camera with gaseous TPC and scintillator
***