I started with a ship full of max-level veterans, and I'm just a complete noob.

On Thursday afternoon of the same week, the fifth batch of single crystals had grown to near the stop line in the quartz crucible of 502.

A section of the high-purity seed crystal sent by Wang Shouwu was cut off, put into a readjusted clamp, and the remaining part was registered according to the length of use, sealed back into the ampoule, and placed in a safe for storage.

This furnace continues to use a pulling speed of 28 revolutions per minute and 0.8 millimeters per minute. The germanium material batch, protective gas flow rate, and furnace chamber pressure are the same as those in the fourth furnace. The only variable that is actively replaced is the new seed crystal with a purity of 99.99% or higher.

Old Sun guarded the transmission box, pressing his palm against the outer casing to check the worm gear meshing, while Fang Xudong connected the motor current, temperature paper tape, and crystal length to the same time axis.

In the latter half of the growth process, the melt level in the quartz crucible continued to decrease, and the axial flow near the bottom of the seed crystal remained stable. Only two narrow peaks caused by actuator repositioning appeared in the temperature control record.

Based on the width of the crescent and the diameter of the crystal column, Jiang Minghe decided to continue lifting for a full hour before instructing Lao Sun to stop the ascent mechanism and maintain rotation to allow the crystal to smoothly detach from the liquid surface.

After the furnace cooled down, a germanium single crystal with a length of nearly fifty millimeters was taken out. The surface growth lines were continuous and the tail end was completely closed, making it the longest crystal pulled out of 502 to date.

Fang Xudong cut off the thin slices at the beginning and end, polished them, and then put them into a polarizing microscope. The changes in brightness and darkness in several directions remained consistent. Then he moved the entire crystal to a four-probe stage and measured the resistivity point by point along the length.

After the curve for the fifth furnace was drawn, the difference between the beginning and end narrowed to nine percent, and the resistivity uniformity remained within a range of about thirty millimeters in the middle section at ±2 percent.

The new seed crystal compressed the head transition zone, while the quartz crucible continued to restrict the input of carbon impurities, thus forming a complete improvement chain with the four curves left from the second to the fifth furnace.

Wu Hanzhang clipped the curve into the 24 gigahertz pre-research plan, pointed to the 30 millimeters in the middle section and said, "Let the materials pass the first test, and the device group will cut it today. Don't let it lie in the cabinet waiting for praise."

Old Sun had already prepared the cutting fixture. He used a soft metal liner to fix the crystal, avoiding the transition area between the beginning and end, and cut the middle section into several thin slices. Fang Xudong took over the grinding and polishing, and then numbered each slice according to its resistivity range.

The point contact process uses tungsten wire styluses ground by Lao Sun. The stylus tip is first inspected under a magnifying glass, and then installed in a spring bracket to make adjustable pressure contact with the surface of the germanium sheet.

After the first round of contact was formed, the difference between the forward and reverse resistances on the test bench was too small. Fang Xudong disassembled the bracket to check and found that the needle tip pressure was too light and the contact area was still in an unstable state.

Old Sun adjusted the spring compression position forward by one notch, while Jiang Ming controlled the pulse amplitude at the low end of the process table to prevent the contact area from being heated too much.

When the second electrical pulse is applied between the probe and the germanium plate, the ammeter pointer swings quickly and then returns. Fang Xudong disconnects the circuit and reconnects it to the DC test terminal, measuring the forward and reverse resistance in sequence.

"The ratio exceeds ten to one."

He wrote the two sets of readings into the device process card, then switched to the simple mixer test bench and connected the signal source, local oscillator input, and intermediate frequency output one by one.

Wu Hanzhang stood beside the test bench and waited for Fang Xudong to complete the calibration before signaling the input. The intermediate frequency meter responded to the input changes, and the conversion loss fell within the expected range. The first point-contact germanium diode thus completed its basic working verification.

A few voices rang out in the research room, but Wu Hanzhang quickly silenced them by raising his hand. He pulled out the official version of the pre-research plan, flipped directly to the device specifications page, and filled in the zero-generation trial production data column by column.

The ratio of reverse resistance to forward resistance has exceeded the minimum threshold, and the mixing conversion loss can also be used for low-level verification. However, the noise figure and reverse breakdown voltage are still far from meeting the requirements of the 24 GHz receiver preamplifier.

"It's usable, but it still falls short of front-end requirements."

Wu Hanzhang pushed the test sheet in front of Jiang Ming and marked the noise coefficient and breakdown voltage columns with a pencil.

"If the purity were even one level higher, the contact pin forming process would have to be refined again. If this device were installed in the final preamplifier, the receiving distance and stability would not be guaranteed."

Jiang Ming wrote "Zero Generation Sample Tube" before the device number and archived it separately from the subsequent finalized devices.

"The zero-generation only proves that domestically produced high-purity germanium can be used to make working devices. Changing both the material and the probe parameters in the next round will confuse the results. We should proceed along two separate lines first."

The material line increased the number of regional purification cycles from six to ten, requiring the Institute of Physics to provide longer quartz tubes and more furnaces. Meanwhile, the device line maintained the fifth furnace of materials, gradually changing the amplitude and duration of electrical pulses to find the process window between contact resistance, noise, and breakdown voltage.

Fang Xudong drew two experimental matrices on the back of the process card. The pulse amplitude was divided into four levels, and each level was matched with three sets of action time. The stylus pressure was kept uniform, and the material sheet was cut from adjacent positions of the same crystal segment.

"Start with twelve sets, and do at least three in each set to eliminate the difference between the needle tip and the needle tip."

After reviewing the required number of germanium wafers, Wu Hanzhang postponed the original assembly time of the entire machine by three days and arranged for the materials group and the device group to use the test bench in staggered shifts.

While we were discussing the furnace application, Comrade Song delivered a reply from the International Exchange Office of the Chinese Academy of Sciences, confirming that Theodore von Kármán's second official reply had been sent via international airmail and was expected to arrive in Pasadena in three to four weeks, according to the flight path.

The receipt also included Qian Xuesen's comments during his review. Fang Xudong unfolded the thin paper and read the line of text word by word.

"The three points of judgment regarding the temperature potential change are clear and independent, and we can continue to prepare for the third communication in this direction."

Jiang Ming tucked the reply slip into the old hardcover memo. The outline of the third communication only listed two items for the time being: material boundary changes and variable cross-section coupling. The specific content still needs to wait for the next round of derivation.

In the late afternoon, as the workday was drawing to a close, Wu Hanzhang took the official version of the 24 GHz pre-research plan to the factory. Factory Director Zhang flipped through the material conditions and device routes to the resource requirements page, and then checked the Aksai fragment summary and the zero-generation sample tube test records.

He wrote "agree to the project" on the cover, and filled in "priority production of materials from the Third Electronics Factory" in the resource guarantee section. He then stamped the factory's seal and returned the plan to Wu Hanzhang.

After this project was approved, the scope of 502's mission officially expanded beyond the original magnetron research. Microwave devices, semiconductor materials, and point contact devices were incorporated into the same pre-research laboratory, and personnel and equipment production schedules were nominally guaranteed by the factory.

When Wu Hanzhang returned to the research lab, in addition to the stamped proposal, he also carried a technical letter forwarded from the semiconductor research group.

Wang Shouwu drew a structural sketch based on the direction of the double crucibles. The inner and outer crucibles, the feeding inlet and the dual-zone heating were arranged. However, the position of the coaxial rotating shaft passing through the furnace cover was repeatedly modified in red pen. The letter directly asked 502 whether he had mastered a reliable vacuum rotary sealing solution.

Wu Hanzhang placed the letter on Jiang Ming's desk and used a cigarette box to weigh down the curled-up letter.

"He spoke up."

Jiang Ming reviewed the shaft diameter, rotational speed, and vacuum requirements in the sketch, then took out the sealing record of the Yuanlei No. 1 permanent magnet assembly from the iron cabinet and turned to the page about the rotating part's through-wall structure.

The experience gained in rotary sealing during magnetron manufacturing can be directly transferred. The original structure uses magnetic fluid to form a sealing ring between multiple pole shoes, which can maintain airtightness and reduce the impact of mechanical friction on shaft stability during low-speed rotation.

He redrawn a small-diameter structure suitable for the double crucible, listing the pole shoe level, magnetic circuit closure, and temperature resistance isolation as design conditions, retaining only the working range that 502 had already verified, and requiring Wang Shouwu to conduct no-load tests on the parts that exceeded it.

At the end of his reply, Jiang Ming briefly explained the concept of magnetohydrodynamic sealing and the verification results of Yuanlei-1, and attached a reduced cross-sectional diagram.

After reading the reply, Wu Hanzhang pushed the device box of the zero-generation sample tube next to the drawings. On one side was the high-purity seed crystal sent by the semiconductor research group, and on the other side was the vacuum rotary sealing scheme submitted by 502.

The two sets of materials were subsequently registered and sealed, and sent to the Institute of Physics through internal exchange channels. The technology that the two parties could exchange also extended from materials and processes to the core structure of the equipment.