A thermonuclear weapon, fusion weapon or hydrogen bomb (H bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation atomic bombs, a more compact size, a lower mass, or a combination of these benefits. Characteristics of nuclear fusion reactions make possible the use of non-fissile depleted uranium as the weapon's main fuel, thus allowing more efficient use of scarce fissile material such as uranium-235 (235U) or plutonium-239 (239Pu). The first full-scale thermonuclear test was carried out by the United States in 1952; the concept has since been employed by most of the world's nuclear powers in the design of their weapons.Modern fusion weapons consist essentially of two main components: a nuclear fission primary stage (fueled by 235U or 239Pu) and a separate nuclear fusion secondary stage containing thermonuclear fuel: the heavy hydrogen isotopes deuterium and tritium, or in modern weapons lithium deuteride. For this reason, thermonuclear weapons are often colloquially called hydrogen bombs or H-bombs.A fusion explosion begins with the detonation of the fission primary stage. Its temperature soars past approximately 100 million kelvin, causing it to glow intensely with thermal X-rays. These X-rays flood the void (the "radiation channel" often filled with polystyrene foam) between the primary and secondary assemblies placed within an enclosure called a radiation case, which confines the X-ray energy and resists its outward pressure. The distance separating the two assemblies ensures that debris fragments from the fission primary (which move much more slowly than X-ray photons) cannot disassemble the secondary before the fusion explosion runs to completion.

The secondary fusion stageconsisting of outer pusher/tamper, fusion fuel filler and central plutonium spark plugis imploded by the X-ray energy impinging on its pusher/tamper. This compresses the entire secondary stage and drives up the density of the plutonium spark plug. The density of the plutonium fuel rises to such an extent that the spark plug is driven into a supercritical state, and it begins a nuclear fission chain reaction. The fission products of this chain reaction heat the highly compressed, and thus super dense, thermonuclear fuel surrounding the spark plug to around 300 million kelvin, igniting fusion reactions between fusion fuel nuclei. In modern weapons fueled by lithium deuteride, the fissioning plutonium spark plug also emits free neutrons which collide with lithium nuclei and supply the tritium component of the thermonuclear fuel.

The secondary's relatively massive tamper (which resists outward expansion as the explosion proceeds) also serves as a thermal barrier to keep the fusion fuel filler from becoming too hot, which would spoil the compression. If made of uranium, enriched uranium or plutonium, the tamper captures fast fusion neutrons and undergoes fission itself, increasing the overall explosive yield. Additionally, in most designs the radiation case is also constructed of a fissile material that undergoes fission driven by fast thermonuclear neutrons. Such bombs are classified as two stage weapons, and most current TellerUlam designs are such fission-fusion-fission weapons. Fast fission of the tamper and radiation case is the main contribution to the total yield and is the dominant process that produces radioactive fission product fallout.Before Ivy Mike, Operation Greenhouse of 1951 was the first American nuclear test series to test principles that led to the development of thermonuclear weapons. Sufficient fission was achieved to boost the associated fusion device, and enough was learned to achieve a full-scale device within a year. The design of all modern thermonuclear weapons in the United States is known as the TellerUlam configuration for its two chief contributors, Edward Teller and Stanislaw Ulam, who developed it in 1951 for the United States, with certain concepts developed with the contribution of physicist John von Neumann. Similar devices were developed by the Soviet Union, United Kingdom, France, and China. The thermonuclear Tsar Bomba was the most powerful bomb ever tested.As thermonuclear weapons represent the most efficient design for weapon energy yield in weapons with yields above 50 kilotons of TNT (210 TJ), virtually all the nuclear weapons of this size deployed by the five nuclear-weapon states under the Non-Proliferation Treaty today are thermonuclear weapons using the TellerUlam design.



China (Chinese: 中国; pinyin: Zhōngguó), officially the People's Republic of China (PRC; Chinese: 中华人民共和国; pinyin: Zhōnghuá Rénmín Gònghéguó), is a country in East Asia. It is the world's most populous country, with a population of more than 1.4 billion. China spans five geographical time zones and borders 14 countries, the second most of any country in the world after Russia. Covering an area of approximately 9.6 million square kilometers (3,700,000 sq mi), it is the world's third or fourth largest country. The country consists of 23 provinces, five autonomous regions, four municipalities, and two Special Administrative Regions (Hong Kong and Macau). The national capital is Beijing.

China emerged as one of the world's first civilizations in the fertile basin of the Yellow River in the North China Plain. China was one of the world's foremost economic powers for most of the two millennia from the 1st until the 19th century. For millennia, China's political system was based on absolute hereditary monarchies, or dynasties, beginning with the semi-legendary Xia dynasty in the 21st century BCE. Since then, China has expanded, fractured, and re-unified numerous times. In the 3rd century BCE, the Qin reunited core China and established the first Chinese empire. The succeeding Han dynasty (206 BCE – 220 CE) saw some of the most advanced technology at that time, including papermaking and the compass, along with agricultural and medical improvements. The invention of gunpowder and movable type in the Tang dynasty (618–907) and Northern Song Dynasty (960–1127) completed the Four Great Inventions. Tang culture spread widely in Asia, as the new Silk Road brought traders to as far as Mesopotamia and the Horn of Africa. The Qing dynasty, China's last dynasty, which formed the territorial basis for modern China, suffered heavy losses to foreign imperialism in the 19th century.

The Chinese monarchy collapsed in 1912 with the Xinhai Revolution, when the Republic of China (ROC) replaced the Qing dynasty. China was invaded by the Empire of Japan during World War II. The Civil War resulted in a division of territory in 1949 when the Chinese Communist Party (CCP) established the People's Republic of China on the mainland while the Kuomintang-led ROC government retreated to the island of Taiwan. Both claim to be the sole legitimate government of China, although the United Nations has recognized the PRC as the sole representation since 1971. China conducted a series of economic reforms since 1978, and entered into the World Trade Organization in 2001.

China is currently governed as a unitary one-party socialist republic by the CCP. China is a permanent member of the United Nations Security Council and a founding member of several multilateral and regional cooperation organizations such as the Asian Infrastructure Investment Bank, the Silk Road Fund, the New Development Bank, the Shanghai Cooperation Organization, and the RCEP, and is a member of the BRICS, the G8+5, the G20, the APEC, and the East Asia Summit. It ranks among the lowest in international measurements of civil liberties, government transparency, freedom of the press, freedom of religion and ethnic minorities. Chinese authorities have been criticized by political dissidents and human rights activists for widespread human rights abuses, including political repression, mass censorship, mass surveillance of their citizens and violent suppression of protests.

China is the world's largest economy by GDP at purchasing power parity, second-largest economy by nominal GDP, and the world's second wealthiest country by total wealth. The country has the fastest growing major economy and is the world's largest manufacturer and exporter. China is a recognized nuclear-weapon state with the world's largest standing army by military personnel and second-largest defense budget.