Subnanosecond pulsed-DC ultra-high gardient photogun for bright relativistic electron bunches

This work is devoted to a novel method for the production of bright, relativistic electron bunches for Laser Wakefield Acceleration. The production of high brightness, ultrarelativistic electron bunches to be used, for example, in X-ray Free- Electron-Lasers is a big challenge for accelerator physicists. Utilization of classical schemes of acceleration leads to significant size of the bunch forming system (injector) and requires large accelerators. This makes it impossible to have such a system available in the laboratory. The only option is to use large facilities shared between many users, and even then, the price of experiments will be high. Therefore novel methods of acceleration and bunch compression have been explored during the last few decades. One of these methods is Laser Wakefield Acceleration, where the acceleration process occurs in a plasma channel. For LWA an injector is needed which produces ultrashort (less than 100 fs) electron bunches. The method investigated in this thesis is based on acceleration of an initially short (25 fs) photo-emitted electron bunch in an extremely high DC field (1 GV/m). To avoid breakdown the acceleration field should be applied for a time shorter than the typical formation time of vacuum breakdown, which is in the range of one nanosecond. For this project it was proposed to use an electrical pulse with a duration of 1 ns and an amplitude of up to 2.5 MV. For production of such a short and high voltage pulse conventional pulsed high voltage generators are not suitable due to many problems related to synchronization, electrical insulation and output pulse reproducibility. Therefore sub nanosecond pulse forming techniques were used in order to create the required output pulse. The main element of this technique is a pulse forming line (PFL), where pulse sharpening and shortening occurs. A Tesla type pulse transformer produces 2.5 MV pulses with (sub-) microsecond duration. The output of the pulsed transformer is switched in a liquid filled spark gap. The PFL is then charged in 5 ns to the 2.5 MV level. The PFL consists of a short storage line and a sharpener discharger to produce pulses with a risetime of around 200 ps. After the sharpener discharger, a cut off discharger reduces the duration to around 1 ns. The pulser was designed and built specially for TU/e at the Efremov institute, St. Petersburg, Russian Federation. During first start up of operation after the system was installed in Eindhoven, we identified several critical points in the design of the pulser. Together these points seriously affected the life time of the entire pulser system. During the first two years of this work the pulser setup was considerably improved. Many parts of the pulser were redesigned and remanufactured. Finally the pulser could be operated for several thousand shots without replacement of the components. In addition, the reproducibility of the output pulses from the transformer was improved from around 20% to about 1%. Variations of the output of the transformer cause instabilities in the breakdown formation in the main liquid spark gap between the transformer and the pulse forming line (PFL). The overall voltage reproducibility achieved at the end of the PFL, i.e. the output of the system, was better than 10%. An acceleration section consisting of a vacuum diode and a beam line setup was designed and built, including several diagnostics. Consideration of the vacuum diode as a part of the PFL showed that the voltage across the acceleration gap can be practically two times higher than the amplitude of the incident pulse (the output pulse of the PFL). This was confirmed later by dark current energy spectra measurements. The maximum registered energy of the electrons was 3.6 MV at 75% of the practical maximum output of the PFL (100% is 2.5 MV), this is the highest registered electron energy for this type of accelerators. For the successful realization of the pulsed DC acceleration concept, a femtosecond laser pulse should arrive on the cathode surface within the applied voltage pulse duration. This imposes strong requirements on the jitter of the whole system, which must be less than 1 ns. For synchronization of the pulser to the laser system we used a laser pulse for the triggering of the main liquid spark gap. The experiments performed showed that even with laser triggering of the liquid spark gap it is impossible to achieve jitter less than the requirements. This is due to the fact that random processes which occur after triggering determine the final breakdown jitter. The best synchronization that was achieved with laser triggering is 29 ns. Photoemission was attempted in a series of several hundred shots. In this series, only two shots with possible photoemission result were detected. The registered charge of these (two) bunches was around 350 pC, close to the expected value. On the basis of this work we identified several critical points of the existing device which must be improved in order to get a suitable setup. Most of them are related to the pulser. As was motioned before, the main issue for stable operation is synchronization, which is mainly determined by the liquid spark gap operation.. To improve the existing situation we propose to use a gas filled spark gap, shorter applied voltage pulses (higher operation frequencies of the pulse transformer), and cylindrical optics for the triggering laser pulse to ionize a larger part of the gap directly by the laser. Another problem is related to the lifetime of the cathode. In our setup the output pulse from the PFL has a long after-pulse with an amplitude up to 1 MV. During this after-pulse the probability of vacuum breakdown in the diode is significant. This significantly decreases the lifetime of the cathode and the reproducibility of the charge of the bunches. To improve this, an active (ohmic) load should be installed in the final part of the PFL. Another possible way to stabilize the current is to use a selfrecovering cathode, such as a liquid metal cathode. In conclusion we can state that the concept of pulsed DC acceleration can be used for the production of ultrashort relativistic electron bunches, but it requires considerable additional engineering research

A compact and portable EMP generator based on Tesla transformer technology

High power electromagnetic pulses are of great importance in a variety of applications such as transient radar, investigations of the effect of strong radio-frequency impulses on electronic systems and modem bio-medical technology. In response to the current trend, a simple, compact, and portable electromagnetic pulse (EMP) radiating source has been developed, based on pulsed transformer technology and capable of producing nanosecond rise-time pulses at voltages exceeding 0.5 MY. For this type of application pulsed transformer technology offers a number of significant advantages over the use of a Marx generator, e.g. design simplicity, compactness and cost effectiveness. The transformer is operated in a dual resonance mode to achieve a high energy transfer efficiency, and although the output voltage inevitably has a slower rise-time than that of a Marx generator, this can be improved by the use of a pulse forming line in conjunction with a fast spark-gap switch. The transformer design is best achieved using a filamentary modeling technique, that takes full account of bulk skin and proximity effects and accurately predicts the self and mutual inductances and winding resistances of the transformer. One main objective of the present research was to achieve a high-average radiated power, for which the radiator has to be operated at a high pulse repetition frequency (pRF), with the key component for achieving this being the spark-gap switch in the primary circuit of the pulsed transformer. Normally a spark-gap switch has a recovery time of about ten milliseconds, and a PRF above 100 Hz is difficult to achieve unless certain special techniques are employed. As the aim of the present study is to develop a compact system, the use of a pump for providing a fluid flow between the electrodes of the spark gap is ruled out, and a novel spark-gap switch was therefore developed based on the principle of corona-stabilization. For simplicity, an omnidirectional dipole-type structure was used as a transmitting antenna. Radiated electric field measurements were performed using a time-derivative sensor, with data being collected by a suitable fast digitizing oscilloscope. Post-numerical processing of the collected data was necessary to remove the ground reflected wave effect. Measurements of the radiated electric field at 10 m from the radiating element indicated a peak amplitude of 12.4 kV/m. Much of the work detailed in the thesis has already been presented in peer reviewed journals and at prestigious international conferences.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Development of a solid state amplifier for the 3rd harmonic cavity for ALBA synchrotron light source

In Synchrotron Light Source facilities with high energy and low emittance electron beams different techniques for improving the quality of the synchrotron light for the users are applied. With this aim ALBA, the Spanish 3rd generation Synchrotron Light Source, is developing a 3rd Harmonic radiofrequency (RF) system as a system additional to the main RF system of the storage ring. This system will consist of four normal conducting active cavities at 1.5 GHz that will provide the required 1.1 MV accelerating voltage to the electron beam and will be fed by four 20 kW power transmitters. This power will be generated by modular Solid State Power Amplifiers (SSPAs) in a continuous wave mode at 1.5 GHz. On the basis of preliminary studies it has been decided that the architecture of each 20 kW power transmitter is a tree diagram made up of primary 1 kW SSPA modules connected in parallel in a combination array. The present PhD thesis is devoted to the design, building and evaluation of a prototype of the 1 kW SSPA module formed four 250 W primary power amplifier modules. Accordingly, all subsystems, namely input and output matching networks of the 250 W primary module, and a four-way power splitter, a four-way power combiner and a novel directivity compensated directional coupler for the non-invasive power monitoring of the 1 kW power amplifier were also designed and their prototypes were tested. A final evaluation of the combined 1 kW SSPA prototype module was successfully carried out and has shown good performance.En las instalaciones de tipo Fuentes de luz de sincrotrón de haz de electrones de alta energía y baja emitancia se aplican diferentes técnicas de mejora de la calidad de la luz de sincrotrón. Con este objetivo, el ALBA, la fuente española de luz de sincrotrón de la tercera generación, está desarrollando un sistema de radiofrecuencia (RF) de la 3ª Harmónica como un sistema adicional al sistema de RF principal del anillo de almacenamiento. Este sistema consistirá de cuatro cavidades activas de conductividad normal de frecuencia 1,5 GHz que suministrarán un voltaje acelerador de 1.1 MV necesario para el haz de electrones y que serán alimentadas por cuatro transmisores de potencia de 20 kW. Esta potencia será generada en modo de onda continua a frecuencia 1.5 GHz por amplificadores de potencia de estado sólido (APES) de estructura modular. A partir de unos estudios preliminares se ha decidido que la arquitectura de cada transmisor de potencia de 20 kW es de tipo diagrama de árbol que consiste de APES primarios de potencia 1 kW conectados en paralelo formando una matriz de combinación. El tema de la presente tesis es el diseño, la construcción y la caracterización de un prototipo del módulo de APES de potencia 1 kW formado por cuatro amplificadores primarios de 250 W de potencia. También, todos subsistemas, concretamente los circuitos de adaptación de entrada y de salida del módulo primario de 250 kW, así como un divisor de cuatro salidas, un combinador de cuatro entradas y un acoplador direccional con una nova solución de compensación de directividad para una monitorización no invasiva han sido diseñados y sus prototipos han sido testeados. La evaluación final de funcionamiento del APES de 1 kW de potencia ha sido realizada con éxito y ha demostrado su buen rendimiento.Postprint (published version

Development of a solid state amplifier for the 3rd harmonic cavity for ALBA synchrotron light source

In Synchrotron Light Source facilities with high energy and low emittance electron beams different techniques for improving the quality of the synchrotron light for the users are applied. With this aim ALBA, the Spanish 3rd generation Synchrotron Light Source, is developing a 3rd Harmonic radiofrequency (RF) system as a system additional to the main RF system of the storage ring. This system will consist of four normal conducting active cavities at 1.5 GHz that will provide the required 1.1 MV accelerating voltage to the electron beam and will be fed by four 20 kW power transmitters. This power will be generated by modular Solid State Power Amplifiers (SSPAs) in a continuous wave mode at 1.5 GHz. On the basis of preliminary studies it has been decided that the architecture of each 20 kW power transmitter is a tree diagram made up of primary 1 kW SSPA modules connected in parallel in a combination array. The present PhD thesis is devoted to the design, building and evaluation of a prototype of the 1 kW SSPA module formed four 250 W primary power amplifier modules. Accordingly, all subsystems, namely input and output matching networks of the 250 W primary module, and a four-way power splitter, a four-way power combiner and a novel directivity compensated directional coupler for the non-invasive power monitoring of the 1 kW power amplifier were also designed and their prototypes were tested. A final evaluation of the combined 1 kW SSPA prototype module was successfully carried out and has shown good performance.En las instalaciones de tipo Fuentes de luz de sincrotrón de haz de electrones de alta energía y baja emitancia se aplican diferentes técnicas de mejora de la calidad de la luz de sincrotrón. Con este objetivo, el ALBA, la fuente española de luz de sincrotrón de la tercera generación, está desarrollando un sistema de radiofrecuencia (RF) de la 3ª Harmónica como un sistema adicional al sistema de RF principal del anillo de almacenamiento. Este sistema consistirá de cuatro cavidades activas de conductividad normal de frecuencia 1,5 GHz que suministrarán un voltaje acelerador de 1.1 MV necesario para el haz de electrones y que serán alimentadas por cuatro transmisores de potencia de 20 kW. Esta potencia será generada en modo de onda continua a frecuencia 1.5 GHz por amplificadores de potencia de estado sólido (APES) de estructura modular. A partir de unos estudios preliminares se ha decidido que la arquitectura de cada transmisor de potencia de 20 kW es de tipo diagrama de árbol que consiste de APES primarios de potencia 1 kW conectados en paralelo formando una matriz de combinación. El tema de la presente tesis es el diseño, la construcción y la caracterización de un prototipo del módulo de APES de potencia 1 kW formado por cuatro amplificadores primarios de 250 W de potencia. También, todos subsistemas, concretamente los circuitos de adaptación de entrada y de salida del módulo primario de 250 kW, así como un divisor de cuatro salidas, un combinador de cuatro entradas y un acoplador direccional con una nova solución de compensación de directividad para una monitorización no invasiva han sido diseñados y sus prototipos han sido testeados. La evaluación final de funcionamiento del APES de 1 kW de potencia ha sido realizada con éxito y ha demostrado su buen rendimiento

DIRECT VOLTAGE MEASUREMENTS USING BULK ACOUSTIC WAVES IN LiNbO3

Accurate (\u3c 1%) direct measurement of high voltage pulse amplitudes above 10 kilovolts becomes challenging due to voltage breakdown limitations in materials, parasitic impedance effects that can distort the pulse shape, and pickup of extraneous signals resulting from electromagnetic interference effects. A piezoelectric crystal-based bulk acoustic wave sensor using lithium niobate (LiNbO3) that has applications to metrology, research, and power metering was developed to overcome these measurement issues with the factors of scalability, ease of use, and compactness in mind. A Y+36° cut LiNbO3crystal was coupled to two acoustic transducers, where direct current (DC) voltages ranging from 128—1100\u2009V were applied transversely to the crystal. An acoustic wave was used to interrogate the crystal before, during, and after voltage application. Both single and multiple pass measurements were performed and compared to linear piezoelectric theory. A comparison study between Y+36° and 0° X-cut LiNbO3 was performed to evaluate the influence of crystal cut on acoustic propagation. The study was extended to applying alternating current (AC), and pulsed voltages. The measured DC data was compared to a 1-D impedance matrix model that was based on a three port circuit with voltage-induced strain effects inputted as a model parameter. An uncertainty budget was carried out for both crystal cuts and compared. Environmental effects such as pressure and temperature were also measured to determine their influence on the sensor under ambient conditions. Published literature regarding material constants, such as elastic constants and piezoelectric constants, for LiNbO3 do not account for the influence of an electric field. In light of this, measurements of the acoustic velocities and material constants under the presence of a DC electric field were performed up to 896 V. This information was used to develop an uncertainty analysis for the determination of stress-charge form piezoelectric constants e15 and e22. All measured and calculated values were input into a Monte Carlo simulation to determine the error of the strain-charge form piezoelectric constants, dij, and how these new values can be used to predict the voltage sensor response

모드 변환된 상대론적인 후방파 발진기

학위논문 (박사)-- 서울대학교 대학원 : 물리·천문학부 물리학전공, 2013. 8. 박건식.Relativistic electron device is a device which generates high power electromagnetic radiation using relativistic electron beam. In our study, the electromagnetic pulse wave (0.5GW-10GHz for 30ns) is normally radiated by using relativistic backward wave oscillator (RBWO) in mildly relativistic regime under 500kV-5kA from relativistic electron device with pulsed magnet system (Max. 3.4Tesla) to focus on relativistic electron beam. Relativistic backward-wave oscillator (RBWO) with relativistic electron beam is capable of producing high-power coherent Cerenkov radiation in the centimeter and millimeter wavelength regimes. The RBWO is designed, fabricated and tested to be operated at 10GHz-Max. 0.5GW level. High power electromagnetic (HPEM) source such as the RBWO has the purpose of transmitting GW-level to specific target. This uses an azimuthally symmetric TM01 waveguide mode for the reason of the characteristic of slow wave structure to interact between relativistic electron beam and backward propagating electromagnetic wave and power capacity to optimize the efficiency. TM01 mode is a doughnut-shaped one with a boresight null due to the cancellation by azimuthally symmetric aperture electric field distribution. In order to focus high-power electromagnetic radiation at the object, it is necessary to be theoretically designed a mode converted antenna which can changes from the TM01 mode to the circularly polarized TE11 mode. The mode converted antenna to be completed on design and fabrication shows that the measured radiation pattern is well matched with the simulated one. In addition, we tested the power estimation of electromagnetic coupling effectiveness on electronic devices at near field range. Relativistic electron device including RBWO, pulsed magnet system and mode converted antenna needs a simultaneously synchronous remote control system with pulsed trigger switch because the discharge and charge characteristic times of respective component devices are different. The remote control system with the software of lab-view is designed, fabricated and tested through several analyses for respective component devices. The study to generate high-power THz radiation source has developed at recent. To increase the frequency of the THz range, some unique physical phenomena with characteristic features including high power THz oversized relativistic backward wave oscillator (RBWO) can be produced. We present an investigation of a coherent Cerenkov radiation (CCR) high power THz source with an oversized slow wave structure of rectangular type. We designed on the cylindrical waveguide structure of a large diameter (D/λ≈8) to generate the power of 0.3GW and to operate at 0.1 THz. The result theoretical design is well matched with the predicted results by a particle-in-cell simulation code, MAGIC 2D with finite difference time domain, CST code.1. Introduction 1.1. Relativistic electron Device 1.2. Relativistic Backward Wave Oscillator (RBWO) 1.3. Issues 1.3.1. Mode conversion antenna 1.3.2. Control system 1.3.3. THz vacuum electronic device (VED) application 1.4. Motivation & Goal 1.5. Outline 1.6. Bibliography 2. Relativistic electron device 2.1. Marx generator 2.1.1. Principle of Marx generator 2.1.2. Test of Marx generator 2.2. Blumlein pulse forming line (PFL) 2.2.1. Principle of Blumlein pulse forming line 2.2.2. Design of Blumlein pulse forming line 2.2.3. Connecting inductor 2.2.4. De-ionized (DI) Water System 2.3. Load 2.3.1. Dummy load 2.3.2. Matching load 2.3.3. The result of load charging and discharging 2.4. Pulsed magnet system 2.4.1. Decision of magnetic field to focus on relativistic e-beam 2.4.2. Design of pulsed magnet power supply 2.4.3. Design of solenoid to generate pulsed magnet field 2.4.4. Magnetic field probe for test 2.4.5. Test of pulsed magnet system 2.5. Design of electron gun 2.5.1. Design of cathode 2.5.2. Design of cathode rod, rod connector and supporter 2.6. Relativistic backward wave oscillator (RBWO) 2.6.1. Design of slow wave structure (SWS) 2.6.2. Resonant reflector 2.6.3. Collector 2.6.4. Simulation for RBWO circuit fabrication 2.6.5. Fabrication of RBWO circuit and cold test 2.7. Bibliography 3. Mode converting antenna 3.1. Design of horn antenna 3.2. Conventional mode converting antenna lens 3.3. Compact design of mode converting antenna lens 3.4. Simulation results for radiation pattern analyses 3.4.1. Conventional mode converting antenna 3.4.2. The flat-plate & convex lens of antenna without mode conversion 3.4.3. The mode converting antenna with three-stepped lens structure and convex lens 3.5. Fabricated mode converting antenna & cold test 3.6. Bibliography 4. Control system 4.1. Synchronous remote control system 4.1.1. Trigger of Marx generator (TMG): triggatron, trigger generator 4.1.2. Adaptor 130 4.1.3. Adaptor test of remote control for Marx generator 4.1.4. Synchronization system for the remote control of relativistic electron device 4.2. Diagnostics 4.2.1. Voltage diagnostic: capacitive voltage probe (CVP) 4.2.2. Current diagnostic in Blumlein PFL 4.2.3. Current diagnostic on the relativistic electron beam 4.2.4. RF coupler to measure RF power from RBWO circuit 4.2.5. RF pick up receiver antenna to measure radiated output RF power 4.2.6. The measurement of the operating frequency 4.3. Integrated mode converted RBWO system 5. Experimental results 5.1. The experimental results of relativistic electron beam 5.2. The experimental results of RF power and the operating frequency from RF measurements system 5.3. The experimental results of radiation pattern by using the mode converting antenna 5.4. Power estimation of electromagnetic coupling effectiveness by mode converted RBWO 5.5. Physical parameter analyses 5.6. Bibliography 6. THz VED application: design of oversized RBWO (0.1THz-0.3GW 30ns) 6.1. Theoretical design of 0.1THz oversized RBWO 6.1.1. Structure and Physical Model 6.1.2. Decision of a Large Diameter in an Oversized Structure 6.1.3. High Current Electron Gun 6.1.4. Dispersion relation and mode selection of slow wave structure under overmoded size 6.1.5. The Resonant Reflector 6.1.6. Collector 6.2. Simulation results 6.2.1. Comparison with basic research of oversized RBWO 6.2.2. Simulation results by PIC simulation (MAGIC 2D code) 6.3. Design of mode converting antenna at 0.1THz 6.4. Bibliography 7. Conclusion Curriculum Vitae Publication List (SCI journals) List of domestic conference papers List of international conference papersDocto

A high-voltage pulsed power modulator for fast-rising arbitrary waveforms

This work presents the design and testing of a new semiconductor-based pulsed power modulator meeting the challenging requirements of a pulsed electron beam device (GESA): a fast-rising (10^12 V/s) output voltage with arbitrary waveform of maximum 120 kV at a maximum current of 600 A for a pulse duration of up to 100 µs

Design and operation of a harmonic gyrotron based on a cusp electron gun

Strathclyde theses - ask staff. Thesis no. : T13121This thesis presents the results of successful operation of a 2nd harmonic gyrotron based on a cusp electron gun. The numerical and experimental results agreed well with the gyrotron design parameters. Two gyrotrons based on a cusp electron gun were designed: the first gyrotron operated at the 2nd harmonic and the second gyrotron was studied to look at the scaling of this concept for operation at the 7th harmonic at a frequency of 390 GHz. The cusp electron gun was used to produce the electron beam in the gyrotron which was annular in shape. The electron beam had a voltage of 40 kV, a current of 1.5A and a velocity ratio (perpendicular component to horizontal component) of 1.5. The experimental results from the first cusp electron gun and measurements of the high quality electron beam with ~8% velocity spread and ~10% alpha spread are presented. Analytical, numerical and experimental results of a DC harmonic gyrotron are presented. The 3D PIC code MAGIC was used to simulate the interaction of the harmonic gyrotron such as the TE71 mode at the 7th cyclotron harmonic with the large orbit electron beam with the beam thickness and beam spread introduced into the simulation. The interaction cavity of both gyrotrons was in the form of a smooth cylindrical waveguide. The relationship between the cavity dimensions and cavity Q values has been studied for optimized output at the design mode with the aim of suppressing other competing modes. A linear output taper was designed with low mode conversion at the gyrotron output. A Vector Network Analyzer with high frequency millmetre wave heads was used to measure the millimeter wave properties of the gyrotron cavity. Experiments were conducted using the electron gun for the harmonic gyrotron. The gyrotron and electron gun were built as well as the interlock and safety system, pulsed power supply and magnet, the cooling and vacuum system. Millimetre wave radiation was measured for the 2.6 mm diameter cavity gyrotron operating at the 2nd harmonic at a magnetic field of 2.08 T. Experiments demonstrated that the harmonic gyrotron was sensitive to the magnetic field and electron beam parameters. Millimetre wave radiation from 108GHz to 110GHz was measured with the use of a W-band rectifying crystal detector and high pass cut off filters. The frequency of the measured millimeter wave radiation agreed very well with the design and predictions of theory.This thesis presents the results of successful operation of a 2nd harmonic gyrotron based on a cusp electron gun. The numerical and experimental results agreed well with the gyrotron design parameters. Two gyrotrons based on a cusp electron gun were designed: the first gyrotron operated at the 2nd harmonic and the second gyrotron was studied to look at the scaling of this concept for operation at the 7th harmonic at a frequency of 390 GHz. The cusp electron gun was used to produce the electron beam in the gyrotron which was annular in shape. The electron beam had a voltage of 40 kV, a current of 1.5A and a velocity ratio (perpendicular component to horizontal component) of 1.5. The experimental results from the first cusp electron gun and measurements of the high quality electron beam with ~8% velocity spread and ~10% alpha spread are presented. Analytical, numerical and experimental results of a DC harmonic gyrotron are presented. The 3D PIC code MAGIC was used to simulate the interaction of the harmonic gyrotron such as the TE71 mode at the 7th cyclotron harmonic with the large orbit electron beam with the beam thickness and beam spread introduced into the simulation. The interaction cavity of both gyrotrons was in the form of a smooth cylindrical waveguide. The relationship between the cavity dimensions and cavity Q values has been studied for optimized output at the design mode with the aim of suppressing other competing modes. A linear output taper was designed with low mode conversion at the gyrotron output. A Vector Network Analyzer with high frequency millmetre wave heads was used to measure the millimeter wave properties of the gyrotron cavity. Experiments were conducted using the electron gun for the harmonic gyrotron. The gyrotron and electron gun were built as well as the interlock and safety system, pulsed power supply and magnet, the cooling and vacuum system. Millimetre wave radiation was measured for the 2.6 mm diameter cavity gyrotron operating at the 2nd harmonic at a magnetic field of 2.08 T. Experiments demonstrated that the harmonic gyrotron was sensitive to the magnetic field and electron beam parameters. Millimetre wave radiation from 108GHz to 110GHz was measured with the use of a W-band rectifying crystal detector and high pass cut off filters. The frequency of the measured millimeter wave radiation agreed very well with the design and predictions of theory