The Device that Won WW2 - The Cavity Magnetron

It was called “the most valuable cargo ever brought to U.S. shores.” and in many ways it sparked many technological aspects of the world we live in today and yet this

device

had a bumpy start and appears to have been invented independently several times in different countries. A couple of years ago I made a video about the proximity fuze shells that gave the Allies a huge advantage in World War II, but there was another piece of technology that worked hand in hand with those that were somehow more important to the war effort and these. These are some of the things that emerged from the development of this

device

.

The detection and tracking of airplanes, spacecraft, missiles and even projectiles in flight, ships at sea, as well as insects and birds in the atmosphere, computer vision systems, mapping the Earth's surface from space and measuring the properties of the atmosphere and oceans to monitor Climate change and the most popular way to cook food quickly. The radar showed the allies what the Germans wanted to keep hidden, but if you want to stay out of the spotlight then you need something that can obfuscate what you are doing and you may not know that NordVPN is not just a VPN service but It also has protection against threats. feature to stop tracking, block malware and intrusive ads, and more.

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The story of how this came about is also unusual because although it was a top secret British innovation, it had actually been invented independently by several other countries before the British finally created one that worked and could be mass produced, and therefore, it ended up being delivered to the Americans as part of the so-called Tizard mission in August 1940. This is the story of the

cavity

magnetron

, a top-secret device that put a stop to the Atlantic submarines that threatened to deprive Great Britain of food. Brittany. and materials, it changed the way the Allies brought air warfare to Germany and also allowed televised diners to fit into our modern-day lifestyles.

Although in its infancy, the electronic warfare of World War II was as important as the cannons, bombs, and shells that were fired. In the Battle of Britain, radar played a key role for the RAF because it was numerically disadvantaged to the Luftwaffe. The radar gave them the advantage because they could see where the Germans were coming from, at what altitude, and the approximate strength of the attacking force, giving them a 15-minute advantage. Once RAF dispatchers had that information, they could move the limited but more capable fighters into positions ready to attack German bomber formations. Because they always seemed to be in the right place at the right time, the Germans thought the RAF had more planes and crews than them.

It was estimated that the tactical advantage it gave the RAF was the equivalent of three times the number of fighters it actually had. While this British early warning radar worked well, it used a series of large 360-foot or 110-meter towers called chain houses that covered the entire European side of Britain. By the time of the Battle of Britain, the Germans had realized that they were part of some kind of early warning system, and attacked to try to destroy it. Although some of the equipment sheds were damaged, the towers survived thanks to their open steel girder construction, and the Luftwaffe concluded that it was too difficult to damage the stations simply by bombing and decided to leave them alone for the rest of the war.

The domestic chain radar used a wavelength of between 10 and 13 meters that could detect groups of aircraft at a distance of up to 100 miles or 160 kilometers, but the wavelength was too long to see finer details. There was an airborne version using a 1.5 meter wavelength in development, but Mark Oliphant, who was a member of the classified British radar program, thought that a radar with a wavelength of 10 centimeters or less and at least 1 kW of power would be much better for the air. wear. The only problem was that they needed a device called a Magnetron capable of producing that, but none were capable of delivering the results.

Back then, there were two ways to generate a microwave signal: you could have a low-power oscillator and amplify it with a klystron, a specialized line-beam vacuum tube, or you could create a high-power oscillator and use it directly. Oliphant used a klystron to generate a 10 cm or 3 Ghz signal with a power of 400 W, but it seemed that it would be impossible to create a sealed pulsed version that would be suitable for aerial use. Back then there were no semiconductors like we have today, everything was made with vacuum tubes or valves as we call them in the UK.

The first types of vacuum tubes were diodes and triodes. A diode valve allows current to flow in one direction from the heater cathode to the anode but not the other. The triode added a grid between the anode and the cathode, applying a small voltage to the grid controlled the current flow from the heater cathode to the anode in proportion to the grid voltage and thus became an amplifier. However, this method of electrostatic control was patented in 1906 by the American Lee De Forest, so the search to find an alternative, non-patented method was underway and the

magnetron

emerged.

This was developed by Albert Hull in 1921 while working at GE to try to get around the Triode valve patent. This used a magnetic field to control the flow of electrons and from there the name arose as the union of “Magnetic” and “Electron”, although the idea worked but was very inefficient. But Hull's papers were taken up by physicists in Germany in 1924, who added an additional cathode, and then by Japanese physicists who noted that it could produce microwave signals with further developments in energy production by the Russians. But it was the British physicists John Randall and Harry Boot from the University of Birmingham, England, in 1940, who took ideas from the Dutch engineer Klaas Posthumus, who had clarified the theoretical functioning of the magnetron.

To this, they added 8 cavities around the central cathode joined by small holes. This effectively created a completely new device that worked in a very different way. The output signal was determined entirely by the physical shape and size of the cameras, rather than by external circuitry or fields. This new device resembled the chamber of a Colt revolver, of which the manufacturing jigs were used to make the prototypes, and was called a

cavity

magnetron. In this, the core is surrounded by a permanent magnet, so the electrons produced by the heated cathode are forced to rotate around the central cavity while the electrons enter the surrounding cavities and start oscillating at a given resonance frequency. due to the size of the cavities.

As more electrons were emitted from the cathode, the microwave frequency signal increased and was then channeled out of the device to an antenna or waveguide. This was a radical change in technology and, for the first time, a device not much larger than the palm of your hand could produce a high-power signal of less than 10 cm that could be mounted on an airplane and display objects on a screen. radar wherever the microwave beam was. was pointed out. The first prototypes produced a wavelength of 9.8 cm with a power output of 400W. The work was handed over to the General Electric Company Research Laboratories in Wembley, London, and within a couple of months they had a device that produced 10 kW of pulsed power.

They also fixed frequency instability that had plagued previous designs. However, Britain at the time was alone in the war and was devoting all its resources to keeping the Germans at bay just across the English Channel and the Battle of Britain was in full swing. This meant that the development and production of new cutting-edge technologies was severely limited. The British government had been calling on the United States to join the war, but they refused, but would provide food and hardware. Henry Tizard, a scientist and chairman of the Committee of Aeronautical Research, who had orchestrated the development of radar before the war, was so concerned about the situation that he convinced Winston Churchill to authorize sending a secret delegation to the United States to offer the Britain's most advanced technology. in exchange for mass development and manufacturing far away from the German threat and one of the devices taken was the latest prototype cavity magnetron manufactured by GEC, serial number 12.

The ramifications of this were great and of all the ideas it presented the Tizard mission. For the United States, including plans for the atomic bomb, the cavity magnetron was the one most coveted by Americans. This was something that was far ahead of what they had been working on and amazed American scientists. The British Cavity magnetron was a thousand times more powerful than the best American microwave transmitter using a klystron at the time and produced precise pulses. American historian James Phinney Baxter III later said: "When members of the Tizard Mission brought a cavity magnetron to the United States in 1940, they carried the most valuable cargo ever brought to our shores." Bell Laboratories took the British sample and began making copies, and by the late 1940s, the Radiation Laboratory or Rad Lab at MIT had been created to develop several types of radar based on the cavity magnetron, from compact units and light for airplanes to early warning systems that were transported in five trucks.

However, concerned that if cavity magnetrons were used in aircraft they might fall into enemy hands, their deployment was delayed by almost 2 years and it was not until 1943 that they were used by ground-based bombers. Like the first proximity shells, they were used over the sea in the Battle of the Atlantic, as there was little chance of enemy and later RAF night fighters operating over the British mainland and the English Channel. recover the downed planes. By 1942, the effect of the new radar on the war was becoming dramatic for the Allies and much worse for the Germans, with one of the greatest effects on the submarine fleets or Wolfpacks that operated in the Atlantic and had sunk millions of tons of submarines.

Allied shipping. Now, Allied aircraft using information from the newly deciphered Enigma codes could search in all weather for submarine command towers on the surface and attack directly or warn convoys where the submarines were. The Allies also knew that all submarines had to return to their bases at some point and that these were mostly located on the Atlantic coast of occupied France. During these trips near the coast, the submarines would surface to replenish their air supply and recharge their batteries with diesel generators, something they did under the cover of darkness. Using the new aircraft-mounted radar, the British Coastal Command would look for submarines returning to and from their highly armored underwater shelters under the cover of darkness and attack them, something that took them by surprise.

It soon became clear to the Germans that entering and leaving submarine bases was now much more dangerous, and as their losses mounted, in late 1943 Admiral Doenitz was forced to reduce U-boat attacks from which he had never encountered. they recovered. Doenitz once boasted that “an airplane can no more kill a submarine than a crow can kill a mole,” something that the new ship-mounted radarplane was proving to be very wrong. The strange thing is that at the beginning of the war, the Germans were leaders in radar technology, but through a decision made directly by Hitler after the fall of France and his confidence that the German army could crush any opposition that was backed by the boss. of the Luftwaffe Hermann Göring, decreed that no scientific investigations would be undertaken unless a conclusive result could be guaranteed within one year.

The German high command simply did not believe that any type of radar the Allies used could have much of an impact on German forces. This would unknowingly put them at a considerable disadvantage just as the Allies were pushing the investigation forward. The British H2S radar was the first “blind aiming radar” capable of finding ground targets without visual assistance and allowed for much more accurate bombing raids even when the target was hidden. A cavity magnetron and a nose-mounted turntable were used for this if the aircraft was first used in January 1943. A few nights later, a Stirling bomber with an H2S on board crashed near Rotterdam.

It was discovered intact by technicians working for Telefunken when the self-destruct explosive failed to explode. The Germans already knew the principle of the cavity magnetron based on work published in Leningrad in 1936 and concluded that the British design was similar to the Russian one, but their failure to follow up and develop their own microwave radar had given the Allies the advantage. . In 1945, after the war, a German replica of the British H2S radar was sent to Britain for analysis and was found to be an almost identical copy of the first British version with some errors, but was not used in combat operations. .

This was not because German technology was inferior, but rather highlighted differences in how German scientists worked or rather did not work well with the high command. While radar was fully integrated into the Allied forces, it was almost non-existent in the German forces. Microwave weapon-laying radars used in conjunction with the newly developed proximity fuze not only made the large guns on Allied battleships much more accurate, but also anti-aircraft guns for attack aircraft. During the V1 flying bomb attacks on London, British radar-controlled anti-aircraft batteries using proximity-fuzed shells were credited with shooting down many of the flying bombs before they reached their target.

Allied use of a cavity magnetron-based radar would have a major impact on the air war with the Luftwaffe and, although it continues to be used in some radar systems, because the output signal changes from pulse to pulse, both in frequency as in phase. , the cavity magnetron was replaced by high-power klystrons and traveling wave tubes for systems requiring high-power, high-precision pulsed outputs, but that was not the end for this device. After the war, Percy Spencer, an American inventor and engineer working for Raytheon, noticed that the chocolate bar in his pocket had melted when he approached a magnetron in Raytheon's laboratories.

Although he didn't know it at the time, he suspected that he had something to do with the microwaves he generated. He began experimenting by holding a bag of popcorn kernels in front of the magnetron and watching them appear in the bag. After much effort, he filed a patent for the world's first microwave oven on October 18, 1945 and although it took 20 years to come down not only in price but also in size, it began the revolution that would lead to the convenient kitchen we know today. take for granted today. Today there are over a billion cavity magnetrons in use to power microwave ovens in most kitchens around the world and I wonder if the inventors of those first magnetrons could have realized how they would change the world for a much greater purpose. peaceful.

So thanks for watching and don't forget to share and subscribe. See you in the next video.