Remember how slowly the sun fuses. Protons last hundreds of millions (maybe billions) of years before they fuse in the conditions at the core of the sun. Of course DD fusion would be faster.
Remember 10nm is 100 Angstroms. LCLS is almost 100X shorter wavelength than that. I don't think there are any other coherent sources near that wavelength.
Yes, room temperature accelerators typically operate with RF pulse lengths from 100 nanoseconds to a few microseconds. Superconducting accelerators typically operate from a millisecond to CW. The LCLS produces a single electron bunch at a repetition rate of up to 120Hz (10Hz at the moment). DESY Flash operates with a train of bunches - I think the design is around 1000 bunches (I don't know how many they have been able to use), at an overall repetition rate of 5Hz.
You get much higher average power from a SC accelerator, a room temperature accelerator is considerably cheaper to build if you don't need the large number of bunches.
You are right, we use the last 1/3 of the linac (about a kilometer) for a 14 GeV beam. The existing structures run at 17MV/M. The same structures can run as high as 35-40 MV/M (used for the positron capture section), but the power consumption is very high. The X-band test structures (for NLC and CLIC) operate at something like 75MV/M (loaded gradient). You could make a considerably shorter machine (maybe 3X) if you needed to, but it would be very expensive to build an entire new accelerator.
The existing and future FELs at DESY use superconducting structures. I think flash operates at something like 20MV/M, and the (future) XFEL is designed for 25MV/M.
I was surprised, but the LCLS laser doesn't make thing fluoresce. We had a camera watching a wavelength calibration foil (Nickel) and didn't see any light at all until we burned through. We don't have a good energy calibration yet, but it is something like a millijoule in 50 femtoseconds.
You can get pretty good reflectivity using glancing incidence mirrors, or crystal mirrors tuned to specific wavelengths. The plan is to focus the LCLS beam to a very small spot to get higher intensities.
FLASH at DESY in Germany has run for several years now. I think their record shortest wavelength was around 30 angstroms. There is a project underway there to build a 1 angstrom laser. LCLS is presently running at 1.5 angstroms.
I don't know if X-ray wavelengths are officially defined, but wikipedia lists 100 to 0.1 angstroms, so all the above machines would count.
It depends on where you draw the line for "X-rays". The LCLS is operating at 1.5 Angstroms (about 8.3 KeV) and is by a lot (factor of 20?) the shortest wavelength coherent source ever built. Storage rings produce X-rays, but they are icoherent and much lower peak power. If anyone has heard of another laser in this wavelength range, please let me know - we'll be happy to correct our info.
Its probably the WORST weapon ever built. A kilometer and a half long. Can only change its aiming point by a fraction of a degree. It took about 15 minutes to burn a pin sized hole in a piece of metal foil, and it only goes a couple of meters through air. Now if the bad guys decide to attack us with very slow moving, really tiny robots, one at a time, maybe we can do something.
Nah, at we have had lots worse: SLAC: formerly Stanford Linear Accelerator Center, now just SLAC. SLC: SLAC Linear Collider (note the nested acronym) NLC: Next Linear Collider - (possibly the worst acronym I've ever seen) FACET - I don't even remember that is - but we are building it.
It IS a big deal. Imagine using sheep to grow human brain tissue? Or, imagine human-ape hybrids (which I seem to recall are thought possible) - what rights would they have? I'm not necessarily against all hybrids, but it is a very slippery slope.
There are a lot of computer jobs that require broad experience. I work at SLAC (2-mile long linear accelerator), and we have a large set of complex software to run the facility. For us long term reliability and supportability is important - just the physical hardware to control the accelerator represents tens or hundreds of millions of dollars - we can't just throw it away every 2 years when some new whiz-bang thing comes out. We need programmers with the maturity (not necessarily related to age - but often is) to write good code, not use the latest toys. The airline industry probably does this to an even larger extent.
Sadly the British are NOT close to the bottom. They are descending fast, but the bottom is a LONG way down - and god help us when we get there. We have the technology to monitor what everyone is doing all of the time. Why strip-search when you can have mm-wave cameras that see through clothes? We will catch ALL the criminals - everyone who acts or thinks in a way that disagrees with the government. It isn't really the government's fault: people are too willing to trade freedom for security.
It takes a while to descend, fuel the airplane / car, taxi back and take-off again. Not the end of the world, but it starts to eat into the speed advantage. I typically loose 1/2 hour in a re-fueling in my plane.
It is true that high resolution images pose some risk: terrorists might be able to use the images to plan more effective attacks, for instance through GPS guided weapons. BUT - almost any useful technology can be used to do harm. It is difficult to think of a technological advance that can't: Fire -> burn villages, Wheel -> war charriots, Metal -> swords, nuclear power -> nuclear weapons, genetic engineering -> engineered diseases. Whether we allow technologies to the public depends on the risk. In this case, the total damage from terrorist attacks in the US is very small - and as far as we can tell, none of it was related to high resolution maps. Why do we feel the need to fix this particular problem?
I agree. I have both linux and windows at home. My wife uses photoshop - has years of experience with it. Why should she want to change to gimp. Even if it can do everything photoshop can do, why spend time learning something new? Compared to her time, the few $100 for photoshop is not significant.
At work documents are handed around in microsoft word format. Openoffice "mostly" reads and writes word, but not always - and after wasting someone else's time trying to use one of my converted documents, I now do everything for work in word.
There are also a lot of aplications that just do not exist for linux. There is no way to download and program my aircraft GPS from linux. The graphic interface to the AOPA flight planning sight doesn't run on linux. These examples are special purpose to me - but other people will have other requirements.
I can't even play a DVD on linux without installing software that I know nothing about, and which comes with various warnings that I may be breaking the law by using it.
General relativity predicts that gravity waves travel at the speed of light. The gravity waves don't come from "inside" the black hole but from gravitational fields of the material collapsing into a black hole. You can also get gravity waves from two colliding black holes (cool!). The event horizons merge and oscillate briefly, emitting some reasonably percentage of the combined mass energy as gravity waves.
There is a lot of evidence for gravity waves from the spin-down of neutron star binaries. It is pretty well accepted that they exist, but no direct observations yet. Webber might have seen something, but I doubt it would pass traditional 4-sigma requirement for a "discovery".
The Minoan stuff on Crete and Santorini is cool. But, it was similar tech level to (and there is considerable evidence for communication with) New Kingdom Egypt of about the same time. The eruption of Thera (Modern Santorini) destroyed the Minoan cities on Santorini, but the cities on Crete were re-built and lasted another couple of hundred years according to carbon dating.
Thank you for posting the information, it is an interesting idea. If I understand correctly, if you were limited by photon counting and the receive antenna collected all of the signal, I think it would provide more data per photon. But, if you are limited by receiver thermal noise I'm not sure. If you have a given receiver noise temperature, and a given total receive antenna size does this improve your data rate? Optical systems can work in single photon counting mode. Radio frequency systems cannot (without exotic technology).
Why does Microsoft make it so difficult to disable auto-run? I understand that many customers may like the feature, but why not a simple control panel entry to stop it? Is it somehow tied with DRM for playing videos? I'm not just griping - they must have some reason for this, anyone know what it is?
There are a lot of ways to spend money to improve safety when you fly. 20 hours of flight training may be a better safety win for many pilots than a better ELT. Whether the new beacons are worth it depends on how much and where you fly.
The compromises required to make an airplane also work at a road-legal and customer-acceptable car tend to result in really poor airplanes. Heavy tires and suspension, sound insulation, transmission, bumpers. Car engines are usually optimized for good efficiency at about 20% power. Aircraft engines normally operate at 60-80% in cruise. In general it is just easier to drive to the airport, get in your plane and fly. Rent a car at the other end. If the cost of a rental car bothers you, you shouldn't be flying.
I'm a scientist working in an unrelated field but I'd still like to see manned space get more funding. If it starts doing something really interesting, I might even join.
Why? To me space is the goal, not the means, but if you want a why: Either there is other intelligent life in the universe, or there is not.
If there isn't it would seem a shame that nothing ever got to see 1-10^-20 of the universe.
If there is intelligent life out there - well most examples from history show that when the guys on the ships meet the guys on the shore, you REALLY want to be the guys on the ships.
Slashdot Mirror
Remember how slowly the sun fuses. Protons last hundreds of millions (maybe billions) of years before they fuse in the conditions at the core of the sun. Of course DD fusion would be faster.
Remember 10nm is 100 Angstroms. LCLS is almost 100X shorter wavelength than that. I don't think there are any other coherent sources near that wavelength.
Yes, room temperature accelerators typically operate with RF pulse lengths from 100 nanoseconds to a few microseconds. Superconducting accelerators typically operate from a millisecond to CW. The LCLS produces a single electron bunch at a repetition rate of up to 120Hz (10Hz at the moment). DESY Flash operates with a train of bunches - I think the design is around 1000 bunches (I don't know how many they have been able to use), at an overall repetition rate of 5Hz. You get much higher average power from a SC accelerator, a room temperature accelerator is considerably cheaper to build if you don't need the large number of bunches.
I finally understand why we search the beamline tunnels before we turn on the accelerator.
You are right, we use the last 1/3 of the linac (about a kilometer) for a 14 GeV beam. The existing structures run at 17MV/M. The same structures can run as high as 35-40 MV/M (used for the positron capture section), but the power consumption is very high. The X-band test structures (for NLC and CLIC) operate at something like 75MV/M (loaded gradient). You could make a considerably shorter machine (maybe 3X) if you needed to, but it would be very expensive to build an entire new accelerator.
The existing and future FELs at DESY use superconducting structures. I think flash operates at something like 20MV/M, and the (future) XFEL is designed for 25MV/M.
I was surprised, but the LCLS laser doesn't make thing fluoresce. We had a camera watching a wavelength calibration foil (Nickel) and didn't see any light at all until we burned through. We don't have a good energy calibration yet, but it is something like a millijoule in 50 femtoseconds.
You can get pretty good reflectivity using glancing incidence mirrors, or crystal mirrors tuned to specific wavelengths. The plan is to focus the LCLS beam to a very small spot to get higher intensities.
FLASH at DESY in Germany has run for several years now. I think their record shortest wavelength was around 30 angstroms. There is a project underway there to build a 1 angstrom laser. LCLS is presently running at 1.5 angstroms.
I don't know if X-ray wavelengths are officially defined, but wikipedia lists 100 to 0.1 angstroms, so all the above machines would count.
It depends on where you draw the line for "X-rays". The LCLS is operating at 1.5 Angstroms (about 8.3 KeV) and is by a lot (factor of 20?) the shortest wavelength coherent source ever built. Storage rings produce X-rays, but they are icoherent and much lower peak power. If anyone has heard of another laser in this wavelength range, please let me know - we'll be happy to correct our info.
Its probably the WORST weapon ever built. A kilometer and a half long. Can only change its aiming point by a fraction of a degree. It took about 15 minutes to burn a pin sized hole in a piece of metal foil, and it only goes a couple of meters through air. Now if the bad guys decide to attack us with very slow moving, really tiny robots, one at a time, maybe we can do something.
Nah, at we have had lots worse:
SLAC: formerly Stanford Linear Accelerator Center, now just SLAC.
SLC: SLAC Linear Collider (note the nested acronym)
NLC: Next Linear Collider - (possibly the worst acronym I've ever seen)
FACET - I don't even remember that is - but we are building it.
It IS a big deal. Imagine using sheep to grow human brain tissue? Or, imagine human-ape hybrids (which I seem to recall are thought possible) - what rights would they have? I'm not necessarily against all hybrids, but it is a very slippery slope.
There are a lot of computer jobs that require broad experience. I work at SLAC (2-mile long linear accelerator), and we have a large set of complex software to run the facility. For us long term reliability and supportability is important - just the physical hardware to control the accelerator represents tens or hundreds of millions of dollars - we can't just throw it away every 2 years when some new whiz-bang thing comes out. We need programmers with the maturity (not necessarily related to age - but often is) to write good code, not use the latest toys. The airline industry probably does this to an even larger extent.
Sadly the British are NOT close to the bottom. They are descending fast, but the bottom is a LONG way down - and god help us when we get there. We have the technology to monitor what everyone is doing all of the time. Why strip-search when you can have mm-wave cameras that see through clothes? We will catch ALL the criminals - everyone who acts or thinks in a way that disagrees with the government. It isn't really the government's fault: people are too willing to trade freedom for security.
It takes a while to descend, fuel the airplane / car, taxi back and take-off again. Not the end of the world, but it starts to eat into the speed advantage. I typically loose 1/2 hour in a re-fueling in my plane.
It is true that high resolution images pose some risk: terrorists might be able to use the images to plan more effective attacks, for instance through GPS guided weapons. BUT - almost any useful technology can be used to do harm. It is difficult to think of a technological advance that can't: Fire -> burn villages, Wheel -> war charriots, Metal -> swords, nuclear power -> nuclear weapons, genetic engineering -> engineered diseases. Whether we allow technologies to the public depends on the risk. In this case, the total damage from terrorist attacks in the US is very small - and as far as we can tell, none of it was related to high resolution maps. Why do we feel the need to fix this particular problem?
I agree. I have both linux and windows at home. My wife uses photoshop - has years of experience with it. Why should she want to change to gimp. Even if it can do everything photoshop can do, why spend time learning something new? Compared to her time, the few $100 for photoshop is not significant. At work documents are handed around in microsoft word format. Openoffice "mostly" reads and writes word, but not always - and after wasting someone else's time trying to use one of my converted documents, I now do everything for work in word. There are also a lot of aplications that just do not exist for linux. There is no way to download and program my aircraft GPS from linux. The graphic interface to the AOPA flight planning sight doesn't run on linux. These examples are special purpose to me - but other people will have other requirements. I can't even play a DVD on linux without installing software that I know nothing about, and which comes with various warnings that I may be breaking the law by using it.
General relativity predicts that gravity waves travel at the speed of light. The gravity waves don't come from "inside" the black hole but from gravitational fields of the material collapsing into a black hole. You can also get gravity waves from two colliding black holes (cool!). The event horizons merge and oscillate briefly, emitting some reasonably percentage of the combined mass energy as gravity waves. There is a lot of evidence for gravity waves from the spin-down of neutron star binaries. It is pretty well accepted that they exist, but no direct observations yet. Webber might have seen something, but I doubt it would pass traditional 4-sigma requirement for a "discovery".
The Minoan stuff on Crete and Santorini is cool. But, it was similar tech level to (and there is considerable evidence for communication with) New Kingdom Egypt of about the same time. The eruption of Thera (Modern Santorini) destroyed the Minoan cities on Santorini, but the cities on Crete were re-built and lasted another couple of hundred years according to carbon dating.
Thank you for posting the information, it is an interesting idea. If I understand correctly, if you were limited by photon counting and the receive antenna collected all of the signal, I think it would provide more data per photon. But, if you are limited by receiver thermal noise I'm not sure. If you have a given receiver noise temperature, and a given total receive antenna size does this improve your data rate? Optical systems can work in single photon counting mode. Radio frequency systems cannot (without exotic technology).
Why does Microsoft make it so difficult to disable auto-run? I understand that many customers may like the feature, but why not a simple control panel entry to stop it? Is it somehow tied with DRM for playing videos? I'm not just griping - they must have some reason for this, anyone know what it is?
There are a lot of ways to spend money to improve safety when you fly. 20 hours of flight training may be a better safety win for many pilots than a better ELT. Whether the new beacons are worth it depends on how much and where you fly.
The compromises required to make an airplane also work at a road-legal and customer-acceptable car tend to result in really poor airplanes. Heavy tires and suspension, sound insulation, transmission, bumpers. Car engines are usually optimized for good efficiency at about 20% power. Aircraft engines normally operate at 60-80% in cruise. In general it is just easier to drive to the airport, get in your plane and fly. Rent a car at the other end. If the cost of a rental car bothers you, you shouldn't be flying.
I'm a scientist working in an unrelated field but I'd still like to see manned space get more funding. If it starts doing something really interesting, I might even join. Why? To me space is the goal, not the means, but if you want a why: Either there is other intelligent life in the universe, or there is not. If there isn't it would seem a shame that nothing ever got to see 1-10^-20 of the universe. If there is intelligent life out there - well most examples from history show that when the guys on the ships meet the guys on the shore, you REALLY want to be the guys on the ships.
They have the guns. But seriously, many people are easily manipulated by fear.